第二章例2-7

#include<stdio.h>
int main(void)
{
	int i,n,sum;

	printf("Enter n:");
	scanf("%d",&n);
	sum=0;
	for(i=1;i<=n;i++){
		sum=sum+i;
	}

	printf("Sum of numbers from 1 to %d is %d\n",n,sum);

	return 0;
}