시간 제한메모리 제한제출정답맞힌 사람정답 비율
1 초 128 MB117394939405242.191%

문제

상근이는 자신의 결혼식에 학교 동기 중 자신의 친구와 친구의 친구를 초대하기로 했다. 상근이의 동기는 모두 N명이고, 이 학생들의 학번은 모두 1부터 N까지이다. 상근이의 학번은 1이다.

상근이는 동기들의 친구 관계를 모두 조사한 리스트를 가지고 있다. 이 리스트를 바탕으로 결혼식에 초대할 사람의 수를 구하는 프로그램을 작성하시오.

입력

첫째 줄에 상근이의 동기의 수 n (2 ≤ n ≤ 500)이 주어진다. 둘째 줄에는 리스트의 길이 m (1 ≤ m ≤ 10000)이 주어진다. 다음 줄부터 m개 줄에는 친구 관계 ai bi가 주어진다. (1 ≤ ai < bi ≤ n) ai와 bi가 친구라는 뜻이며, bi와 ai도 친구관계이다. 

출력

첫째 줄에 상근이의 결혼식에 초대하는 동기의 수를 출력한다.

예제 입력 1

6
5
1 2
1 3
3 4
2 3
4 5

예제 출력 1

3

예제 입력 2

6
5
2 3
3 4
4 5
5 6
2 5

예제 출력 2

0

힌트

예제 1의 경우 2와 3은 상근이의 친구이다. 또, 3과 4는 친구이기 때문에, 4는 상근이의 친구의 친구이다. 5와 6은 친구도 아니고, 친구의 친구도 아니다. 따라서 2, 3, 4 3명의 친구를 결혼식에 초대한다.

[{"problem_id":"5567","problem_lang":"0","title":"\uacb0\ud63c\uc2dd","description":"<p>\uc0c1\uadfc\uc774\ub294 \uc790\uc2e0\uc758 \uacb0\ud63c\uc2dd\uc5d0 \ud559\uad50 \ub3d9\uae30 \uc911 \uc790\uc2e0\uc758 \uce5c\uad6c\uc640 \uce5c\uad6c\uc758 \uce5c\uad6c\ub97c \ucd08\ub300\ud558\uae30\ub85c \ud588\ub2e4. \uc0c1\uadfc\uc774\uc758 \ub3d9\uae30\ub294 \ubaa8\ub450 N\uba85\uc774\uace0, \uc774 \ud559\uc0dd\ub4e4\uc758 \ud559\ubc88\uc740 \ubaa8\ub450 1\ubd80\ud130 N\uae4c\uc9c0\uc774\ub2e4. \uc0c1\uadfc\uc774\uc758 \ud559\ubc88\uc740 1\uc774\ub2e4.<\/p>\r\n\r\n<p>\uc0c1\uadfc\uc774\ub294 \ub3d9\uae30\ub4e4\uc758 \uce5c\uad6c \uad00\uacc4\ub97c \ubaa8\ub450 \uc870\uc0ac\ud55c \ub9ac\uc2a4\ud2b8\ub97c \uac00\uc9c0\uace0 \uc788\ub2e4. \uc774 \ub9ac\uc2a4\ud2b8\ub97c \ubc14\ud0d5\uc73c\ub85c \uacb0\ud63c\uc2dd\uc5d0 \ucd08\ub300\ud560 \uc0ac\ub78c\uc758 \uc218\ub97c \uad6c\ud558\ub294 \ud504\ub85c\uadf8\ub7a8\uc744 \uc791\uc131\ud558\uc2dc\uc624.<\/p>\r\n","input":"<p>\uccab\uc9f8 \uc904\uc5d0 \uc0c1\uadfc\uc774\uc758 \ub3d9\uae30\uc758 \uc218 n (2 &le; n &le; 500)\uc774 \uc8fc\uc5b4\uc9c4\ub2e4. \ub458\uc9f8 \uc904\uc5d0\ub294 \ub9ac\uc2a4\ud2b8\uc758 \uae38\uc774 m (1 &le; m &le; 10000)\uc774 \uc8fc\uc5b4\uc9c4\ub2e4. \ub2e4\uc74c \uc904\ubd80\ud130 m\uac1c \uc904\uc5d0\ub294 \uce5c\uad6c \uad00\uacc4 a<sub>i<\/sub> b<sub>i<\/sub>\uac00 \uc8fc\uc5b4\uc9c4\ub2e4. (1 &le; a<sub>i<\/sub> &lt; b<sub>i<\/sub> &le; n) a<sub>i<\/sub>\uc640 b<sub>i<\/sub>\uac00 \uce5c\uad6c\ub77c\ub294 \ub73b\uc774\uba70, b<sub>i<\/sub>\uc640 a<sub>i<\/sub>\ub3c4 \uce5c\uad6c\uad00\uacc4\uc774\ub2e4.&nbsp;<\/p>\r\n","output":"<p>\uccab\uc9f8 \uc904\uc5d0 \uc0c1\uadfc\uc774\uc758 \uacb0\ud63c\uc2dd\uc5d0 \ucd08\ub300\ud558\ub294 \ub3d9\uae30\uc758 \uc218\ub97c \ucd9c\ub825\ud55c\ub2e4.<\/p>\r\n","hint":"<p>\uc608\uc81c 1\uc758 \uacbd\uc6b0 2\uc640 3\uc740 \uc0c1\uadfc\uc774\uc758 \uce5c\uad6c\uc774\ub2e4. \ub610, 3\uacfc 4\ub294 \uce5c\uad6c\uc774\uae30 \ub54c\ubb38\uc5d0, 4\ub294 \uc0c1\uadfc\uc774\uc758 \uce5c\uad6c\uc758 \uce5c\uad6c\uc774\ub2e4. 5\uc640 6\uc740 \uce5c\uad6c\ub3c4 \uc544\ub2c8\uace0, \uce5c\uad6c\uc758 \uce5c\uad6c\ub3c4 \uc544\ub2c8\ub2e4. \ub530\ub77c\uc11c 2, 3, 4 3\uba85\uc758 \uce5c\uad6c\ub97c \uacb0\ud63c\uc2dd\uc5d0 \ucd08\ub300\ud55c\ub2e4.<\/p>\r\n","original":"0","html_title":"0","problem_lang_tcode":"Korean"},{"problem_id":"5567","problem_lang":"2","title":"\u30d1\u30fc\u30c6\u30a3\u30fc","description":"<p>\u3042\u306a\u305f\u306f\u30af\u30ea\u30b9\u30de\u30b9\u30d1\u30fc\u30c6\u30a3\u30fc\u306b\u5b66\u6821\u5185\u306e\u81ea\u5206\u306e\u53cb\u9054\u3068\uff0c\u81ea\u5206\u306e\u53cb\u9054\u306e\u53cb\u9054\u3092\u62db\u5f85\u3059\u308b\u3053\u3068\u306b\u3057\u305f\uff0e \u3042\u306a\u305f\u306e\u901a\u3046\u5b66\u6821\u306e\u751f\u5f92\u6570\u306f n \u4eba\u3067\u3042\u308a\uff0c\u305d\u308c\u305e\u308c\u306e\u751f\u5f92\u306b\u306f 1 \u304b\u3089 n \u307e\u3067\u306e\u756a\u53f7\u304c\u5272\u308a\u632f\u3089\u308c\u3066\u3044\u308b\uff0e \u3042\u306a\u305f\u306e\u756a\u53f7\u306f 1 \u3067\u3042\u308b\uff0e \u3042\u306a\u305f\u306e\u624b\u5143\u306b\u306f\uff0c\u8ab0\u3068\u8ab0\u304c\u53cb\u9054\u3067\u3042\u308b\u304b\u3092\u8a18\u3057\u305f\u30ea\u30b9\u30c8\u304c\u3042\u308b\uff0e \u3053\u306e\u30ea\u30b9\u30c8\u3092\u3082\u3068\u306b\uff0c \u3042\u306a\u305f\u304c\u30af\u30ea\u30b9\u30de\u30b9\u30d1\u30fc\u30c6\u30a3\u30fc\u306b\u62db\u5f85\u3059\u308b\u751f\u5f92\u6570\u3092\u6c42\u3081\u308b\u30d7\u30ed\u30b0\u30e9\u30e0\u3092\u4f5c\u6210\u305b\u3088\uff0e<\/p>\r\n","input":"<p>\u5165\u529b\u306e1 \u884c\u76ee\u306b\u306f\u5b66\u6821\u306e\u751f\u5f92\u6570 n \uff082 \u2266 n \u2266 500\uff09\u304c\uff0c 2 \u884c\u76ee\u306b\u306f\u30ea\u30b9\u30c8\u306e\u9577\u3055 m \uff081 \u2266 m \u2266 10000\uff09\u304c\u66f8\u304b\u308c\u3066\u3044\u308b\uff0e \u5165\u529b\u306f\u5168\u90e8\u3067 2+m \u884c\u304b\u3089\u306a\u308b\uff0e2+i \u884c\u76ee\uff081 \u2266 i \u2266 m\uff09\u306b\u306f 2 \u3064\u306e\u6574\u6570 a<sub>i<\/sub> \u3068 b<sub>i<\/sub> \uff081 \u2266 a<sub>i<\/sub> \uff1c b<sub>i<\/sub> \u2266 n\uff09\u304c\u7a7a\u767d\u533a\u5207\u308a\u3067\u66f8\u304b\u308c\u3066\u304a\u308a\uff0c\u756a\u53f7 a<sub>i<\/sub> \u3068\u756a\u53f7 b<sub>i<\/sub> \u306e\u751f\u5f92\u304c\u53cb\u9054\u540c\u58eb\u3067\u3042\u308b\u3053\u3068\u3092\u8868\u3059\uff0e \u5165\u529b\u306e 3 \u884c\u76ee\u304b\u3089 2+m \u884c\u76ee\u306b\u306f\u540c\u3058\u53cb\u9054\u95a2\u4fc2\u3092\u8868\u3059\u884c\u304c\u91cd\u8907\u3057\u3066\u73fe\u308c\u308b\u3053\u3068\u306f\u306a\u3044\uff0e<\/p>\r\n","output":"<p>\u51fa\u529b\u306f\uff0c\u3042\u306a\u305f\u304c\u30af\u30ea\u30b9\u30de\u30b9\u30d1\u30fc\u30c6\u30a3\u30fc\u306b\u62db\u5f85\u3059\u308b\u751f\u5f92\u6570\u306e\u307f\u3092\u542b\u3080 1 \u884c\u304b\u3089\u306a\u308b\uff0e<\/p>\r\n","hint":"<p>\u5165\u529b\u4f8b 1 \u306b\u304a\u3044\u3066\uff0c\u3042\u306a\u305f\u306e\u53cb\u9054\u306f\u756a\u53f7 2 \u3068\u756a\u53f7 3 \u306e\u751f\u5f92\u306e 2 \u4eba\u3067\u3042\u308b\uff0e \u307e\u305f\uff0c\u756a\u53f7 3 \u3068\u756a\u53f7 4 \u306e\u751f\u5f92\u306f\u53cb\u9054\u540c\u58eb\u3067\u3042\u308b\u306e\u3067\uff0c \u756a\u53f7 4 \u306e\u751f\u5f92\u306f\u3042\u306a\u305f\u306e\u53cb\u9054\u306e\u53cb\u9054\u3067\u3042\u308b\uff0e \u756a\u53f7 5 \u3068\u756a\u53f7 6 \u306e\u751f\u5f92\u306f\u3042\u306a\u305f\u306e\u53cb\u9054\u3067\u3082\u306a\u304f\uff0c\u3042\u306a\u305f\u306e\u53cb\u9054\u306e\u53cb\u9054\u3067\u3082\u306a\u3044\uff0e \u3057\u305f\u304c\u3063\u3066\uff0c\u3042\u306a\u305f\u306f\u756a\u53f7 2,3,4 \u306e 3 \u4eba\u306e\u751f\u5f92\u3092\u30af\u30ea\u30b9\u30de\u30b9\u30d1\u30fc\u30c6\u30a3\u30fc\u306b\u62db\u5f85\u3059\u308b\uff0e<\/p>\r\n\r\n<p>\u5165\u529b\u4f8b 2 \u306b\u304a\u3044\u3066\uff0c\u3042\u306a\u305f\u306b\u306f\u53cb\u9054\u306f\u3044\u306a\u3044\uff0e \u3057\u305f\u304c\u3063\u3066\uff0c\u3042\u306a\u305f\u304c\u30af\u30ea\u30b9\u30de\u30b9\u30d1\u30fc\u30c6\u30a3\u30fc\u306b\u62db\u5f85\u3059\u308b\u751f\u5f92\u6570\u306f 0 \u4eba\u3067\u3042\u308b\uff0e<\/p>\r\n","original":"1","html_title":"0","problem_lang_tcode":"Japanese"}]

출처

Olympiad > Japanese Olympiad in Informatics > Japanese Olympiad in Informatics Qualification Round > JOI 2010 예선 3번