习题5

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

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

    printf("Enter n:");
    scanf("%d",&n);
    for(i=1;i<=n;i++){
        item=(flag*i)/denominator;
        sum=sum+item;
        flag=-flag;
        denominator=denominator+2;
    }
    printf("sum=%.2f
",sum);


    return 0;
}