#include
     
      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;}