第二章例2-8

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

	printf("Enter n:");
	scanf("%d",&n);

	flag=1;
	denominator=1;
	sum=0;

	for(i=1;i<=n;i++){
	  item=flag*1.0/denominator;
	  sum=sum+item;
	  flag=-flag;
	  denominator=denominator+2;

	}
	printf("sum=%f\n",sum);

	return 0;
}