/* Sum of series - Program to calculate sum of series 1/2 - 3/4 + 5/6 - 7/8 ....... upto n terms  -  June 2014 */

#include  <stdio.h>
#include  <conio.h>

void main()
{
    int  i, n ;
    float  k, s=0 ;
    clrscr() ;
    printf("Enter n: ") ;
    scanf("%d", &n) ;
    /* i keeps track of term count , whereas k is used for calculation purpose */
    for(i=1, k=1 ; i<=n ; i++, k=k+2)
        {
            if(i%2==1)
                s=s + k/(k+1) ;
            else
                s=s - k/(k+1) ;
        }
    /* k has to be float in the above expression. If k is int then s will remain zero  */
    printf("Sum of the required series is %f", s) ;
    getch() ;
}

/*
Output :

Enter n: 4
Sum of the required series is -0.291667

*/