#include <stdio.h>
int main(void)
{
    int  i, n, sum;
    printf("Input n:");
    scanf("%d", &n);
    sum = 0;                    /* 累加和变量初始化为0 */
    i = 1;
    while (i <= n)
    {
        sum = sum + i;          /* 做累加运算 */
        i++;    /* 累加计数器加1 */
    }
    printf("sum = %d\n", sum);
    return 0;
}