시간 제한 메모리 제한 제출 정답 맞은 사람 정답 비율
1 초 128 MB 1249 925 820 75.996%

문제

도미노는 여러 종류의 타일 게임에서 사용하는 조각이다. 도미노 조각에는 두 칸으로 이루어져 있다. 각 칸에는 점이 찍혀있는데, 점이 안 찍혀져 있을 수도 있다. 점의 개수는 세트의 크기에 의해서 결정된다. 세트의 크기가 N인 도미노 세트에서 점의 개수는 0보다 크거나 같고, N보다 작거나 같다. 두 도미노에 찍혀잇는 점의 개수가 같다면, 두 도미노는 동일한 것이다. 예를 들어, 점이 2개와 8개 찍혀있는 도미노는 8개와 2개 찍혀있는 도미노와 같은 도미노이다.

크기가 N인 도미노 세트는 N 또는 그보다 작거나 같은 점을 포함하는 가능한 도미노를 모두 포함하고 있고, 각 도미노는 중복되지 않는다. 다음은 크기가 2인 도미노 세트이다.

N을 입력받은 뒤, 크기가 N인 도미노 세트에는 점이 몇 개 찍혀 있는지 구하는 프로그램을 작성하시오.

입력

첫째 줄에 도미노 세트의 크기 N (1 ≤ N ≤ 1000)이 주어진다.

출력

크기가 N인 도미노 세트에 찍혀있는 점의 개수를 출력한다.

예제 입력 1

2

예제 출력 1

12
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