시간 제한 메모리 제한 제출 정답 맞은 사람 정답 비율
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문제

상근이는 생일 선물로 장난감 탱크 N개를 받았다. 탱크를 가지고 놀기 전장을 만들었다. 전장은 나무판 위에 N행 N열 크기로 만들었다.

각 탱크가 한 번에 움직일 수 칸은 인접한 네 칸이다. 탱크는 같은 행과 열에 있는 모든 칸을 공격할 수 있다. 따라서, 탱크는 자신이 있는 칸에 해당하는 행과 열을 보호하고 있다고 말할 수 있다.

두 탱크가 동시에 같은 정사각형 안에 있을 수는 없다.

이렇게 탱크를 가지고 두~세시간 동안 열심히 놀고 있었다. 상근이의 어머니는 점심까지 거르면서 놀고있는 상근이를 못마땅하게 생각했고, 당장 점심을 먹으러 오라고 소리쳤다. 상근이는 탱크가 모든 행과 열을 보호하게 배치를 바꾼 다음에 점심을 먹으러 가려고 한다. (즉, 각각의 행과 열에 하나의 탱크만 있어야 한다)

이렇게 배치를 바꾸는 경우에 탱크를 움직이는 횟수를 적게 하려고 한다.

탱크를 몇 번 움직이면, 각 행과 열에 있는 탱크가 하나가 되는지 구하는 프로그램을 작성하시오. 움직이는 방법이 여러 가지라면 탱크를 움직이는 횟수가 가장 작은 것을 찾는다.

입력

첫째 줄에 탱크의 수 N이 주어진다. (5 ≤ N ≤ 500)

다음 N개 줄에는 각 탱크가 있는 행의 번호 R과 열의 번호 C가 주어진다. (1 ≤ R, S ≤ N) 행과 열은 1부터 N까지 번호가 매겨져 있으며, 위에서 아래, 왼쪽에서 오른쪽 순서이다. 두 탱크가 같은 칸에 있는 경우는 없다.

출력

첫째 줄에 탱크를 몇 번 이동시키면 되는지를 출력한다. 이 값을 K라고 한다.

다음 K개 줄에는 어떤 탱크를 어느 방향으로 움직이는지 출력한다. 가장 먼저 주어지는 탱크의 번호는 1번이고, 나머지 탱크는 순서대로 2, 3, ..., N번이다. 방향은 왼쪽으로 이동할 때는 'L', 오른쪽은 'R', 위는 'U', 아래는 'D'로 출력한다.

정답은 여러 가지일 수도 있다.

예제 입력 1

5
1 1
1 2
1 3
1 4
1 5

예제 출력 1

10
1 D
2 D
3 D
4 D
1 D
2 D
3 D
1 D
2 D
1 D
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(\uc989, \uac01\uac01\uc758 \ud589\uacfc \uc5f4\uc5d0 \ud558\ub098\uc758 \ud0f1\ud06c\ub9cc \uc788\uc5b4\uc57c \ud55c\ub2e4)<\/p>\r\n\r\n<p>\r\n\t\uc774\ub807\uac8c \ubc30\uce58\ub97c \ubc14\uafb8\ub294 \uacbd\uc6b0\uc5d0 \ud0f1\ud06c\ub97c \uc6c0\uc9c1\uc774\ub294 \ud69f\uc218\ub97c \uc801\uac8c \ud558\ub824\uace0 \ud55c\ub2e4.<\/p>\r\n\r\n<p>\r\n\t\ud0f1\ud06c\ub97c \uba87 \ubc88 \uc6c0\uc9c1\uc774\uba74, \uac01 \ud589\uacfc \uc5f4\uc5d0 \uc788\ub294 \ud0f1\ud06c\uac00 \ud558\ub098\uac00 \ub418\ub294\uc9c0 \uad6c\ud558\ub294 \ud504\ub85c\uadf8\ub7a8\uc744 \uc791\uc131\ud558\uc2dc\uc624. \uc6c0\uc9c1\uc774\ub294 \ubc29\ubc95\uc774 \uc5ec\ub7ec \uac00\uc9c0\ub77c\uba74 \ud0f1\ud06c\ub97c \uc6c0\uc9c1\uc774\ub294 \ud69f\uc218\uac00 \uac00\uc7a5 \uc791\uc740 \uac83\uc744 \ucc3e\ub294\ub2e4.<\/p>\r\n","input":"<p>\r\n\t\uccab\uc9f8 \uc904\uc5d0 \ud0f1\ud06c\uc758 \uc218 N\uc774 \uc8fc\uc5b4\uc9c4\ub2e4. (5 &le; N &le; 500)<\/p>\r\n\r\n<p>\r\n\t\ub2e4\uc74c N\uac1c \uc904\uc5d0\ub294 \uac01 \ud0f1\ud06c\uac00 \uc788\ub294 \ud589\uc758 \ubc88\ud638 R\uacfc \uc5f4\uc758 \ubc88\ud638 C\uac00 \uc8fc\uc5b4\uc9c4\ub2e4. (1 &le; R, S &le; N) \ud589\uacfc \uc5f4\uc740 1\ubd80\ud130 N\uae4c\uc9c0 \ubc88\ud638\uac00 \ub9e4\uaca8\uc838 \uc788\uc73c\uba70, \uc704\uc5d0\uc11c \uc544\ub798, \uc67c\ucabd\uc5d0\uc11c \uc624\ub978\ucabd \uc21c\uc11c\uc774\ub2e4. \ub450 \ud0f1\ud06c\uac00 \uac19\uc740 \uce78\uc5d0 \uc788\ub294 \uacbd\uc6b0\ub294 \uc5c6\ub2e4.<\/p>\r\n","output":"<p>\r\n\t\uccab\uc9f8 \uc904\uc5d0 \ud0f1\ud06c\ub97c \uba87 \ubc88 \uc774\ub3d9\uc2dc\ud0a4\uba74 \ub418\ub294\uc9c0\ub97c \ucd9c\ub825\ud55c\ub2e4. \uc774 \uac12\uc744 K\ub77c\uace0 \ud55c\ub2e4.<\/p>\r\n\r\n<p>\r\n\t\ub2e4\uc74c K\uac1c \uc904\uc5d0\ub294 \uc5b4\ub5a4 \ud0f1\ud06c\ub97c \uc5b4\ub290 \ubc29\ud5a5\uc73c\ub85c \uc6c0\uc9c1\uc774\ub294\uc9c0 \ucd9c\ub825\ud55c\ub2e4. \uac00\uc7a5 \uba3c\uc800 \uc8fc\uc5b4\uc9c0\ub294 \ud0f1\ud06c\uc758 \ubc88\ud638\ub294 1\ubc88\uc774\uace0, \ub098\uba38\uc9c0 \ud0f1\ud06c\ub294 \uc21c\uc11c\ub300\ub85c 2, 3, ..., N\ubc88\uc774\ub2e4. \ubc29\ud5a5\uc740 \uc67c\ucabd\uc73c\ub85c \uc774\ub3d9\ud560 \ub54c\ub294 &#39;L&#39;, \uc624\ub978\ucabd\uc740 &#39;R&#39;, \uc704\ub294 &#39;U&#39;, \uc544\ub798\ub294 &#39;D&#39;\ub85c \ucd9c\ub825\ud55c\ub2e4.<\/p>\r\n\r\n<p>\r\n\t\uc815\ub2f5\uc740 \uc5ec\ub7ec \uac00\uc9c0\uc77c \uc218\ub3c4 \uc788\ub2e4.<\/p>\r\n","hint":"","original":"0","problem_lang_code":"\ud55c\uad6d\uc5b4"},{"problem_id":"3043","problem_lang":"1","title":"TENKICI","description":"<p>Mirko found a collection of N toy tanks dating back to the Second World War on his grandfather&#39;s attic. He promptly called his friend Slavko to play with him. They made a battlefield &ndash; a wooden board consisting of squares in N rows and N columns.&nbsp;<\/p>\r\n\r\n<p>Each tank can be moved to one of the four neighbouring squares in a single move. A tank can shoot at any square in the same row and column. The tank is said to be guarding the row and column it is in.&nbsp;<\/p>\r\n\r\n<p>Additionally, no two tanks can be in the same square at any time.&nbsp;<\/p>\r\n\r\n<p>After many hours of play and two previous attempts, Mirko&#39;s mom yelled at them to come down for lunch again, and they decided to rearrange the tanks so that each tank guards a different row and column (meaning also that each row and column contains only one tank).&nbsp;<\/p>\r\n\r\n<p>However, they want to do this using the minimum number of moves.&nbsp;<\/p>\r\n\r\n<p>Write a program that finds the minimum number of moves required to rearrange the tanks so that each row and each column contains a single tank, and one such shortest sequence of moves.&nbsp;<\/p>\r\n","input":"<p>The first line of input contains the integer N (5 &le; N &le; 500).&nbsp;<\/p>\r\n\r\n<p>Each of the following N lines contains two integers R and C (1 &le; R, S &le; N), the row and column of a single tank at the moment of mom&#39;s call. No two tanks are on the same square.&nbsp;<\/p>\r\n\r\n<p>Rows and columns are marked 1 through N, top-down and left-to-right.&nbsp;<\/p>\r\n","output":"<p>Output the minimum number of moves (call this number K) on the first line.&nbsp;<\/p>\r\n\r\n<p>Each of the next K lines should contain the tank being moved and the direction it is moved in, separated by a single space.&nbsp;<\/p>\r\n\r\n<p>Tanks are numbered 1 through N, in the order in which they are given in the input.&nbsp;<\/p>\r\n\r\n<p>The direction can be one of four uppercase letters: &#39;L&#39; for left, &#39;R&#39; for right, &#39;U&#39; for up and &#39;D&#39; for down.&nbsp;<\/p>\r\n\r\n<p>Note: The sequence need not be unique.&nbsp;<\/p>\r\n","hint":"","original":"1","problem_lang_code":"\uc601\uc5b4"}]