hdu1001

n*（n+1）可能超过一个int长度  分开

#include<stdio.h>int main(){    int n;    while(scanf("%d",&n)!=EOF)    {        if(n%2==0)           printf("%d\n\n",(n/2)*(n+1));        else           printf("%d\n\n",n*((n+1)/2));    }    return 0;}