#include <stdio.h>

int main(void)
{
	int a, b, N;
	a = 0;
	b = 0;
	printf("nを入力して下さい\n");
	scanf("%d", &N);
	while (a < N) {
		a++;
		b = b + a;
	}
	printf("合計は%d", b);
	return 0;
}