编辑代码

#include <stdio.h>
int sum(int x);
int main ()
 {
    int n=10;
    printf("输入n的值：");
    scanf("%d",&n);
    printf("1到%d的和%d\n",n,sum(n));
    printf("1到15的和%d\n",sum(15));
    return 0;
}  

int sum(int x)
{
int s=0,i;
for(i=1;i<=x;i++)
    s=s+i;
return s;
}