2-8

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

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