http://acm.hdu.edu.cn/showproblem.php?pid=1001
# include <stdio.h>
int main ()
{
int n;
while(scanf("%d",&n) != EOF)
{
int Sum = 0;
for(int i = 1; i <= n; i++)
Sum += i;
printf("%d\n\n",Sum);
}
return 0;
}
原文：http://www.cnblogs.com/linjiaman/p/4296560.html