#include<stdio.h>
#include<stdlib.h>
int main(void){
	int  N,n,sum;
	printf("请输入孩子数量\n");
	scanf("%d",&N);
	if(1<=N<=100)
	{sum=0;
	for(n=1;n<=N;n=n+1)
	{sum=sum+n;	
	}	
	}else if(N<=1&N>=100); {
	printf("输入错误\n",sum);
	return n;
	}
	printf("Sum is %d.\n",sum);

    return 0;
	}
   