OI-source/history_source/信息学奥赛一本通/1.6.2.1t.cpp

#include<cstdio>
using namespace std;
int f(int n)
{
	if(n==1) return 1;
	return n+f(n-1);
}
int main()
{
	int n;
	scanf("%d",&n);
	printf("%d\n",f(n));
	return 0;
}