S = 1 - 2 + 3 - 4 ..... ± N

Calculate the value of  this sum series [ S = 1 - 2 + 3 - 4 ... ± N ] 

Source code :-

#include<stdio.h>

int main()

{

    int i,n,s=0,j=1;

    printf("Enter the value of n: ");

    scanf("%d",&n);

    for(i=1;i<=n;i++)

    {

        s=s+(i*j);

        j=(j*(-1));

    }

    printf("Answer is => %d",s);

    return 1;

}

Input-Output :-

abhi@hp-15q-laptop:~$ gcc ss.c

abhi@hp-15q-laptop:~$ ./a.out

Enter the value of n: 5

Answer is => 3