135.c

来自「平时acm训练时ac的源代码」· C语言 代码 · 共 16 行

/*
135
Accepted 56 ms 114 kb 
*/

#include <stdio.h>

int main()
{
	unsigned long N;
	scanf("%lu", &N);
	N = N*(N+1);
	N = N/2;
	printf("%lu", N+1);
}