# How to Get Sum of Series 1-2+3-4+…. +n in C Program

It is easy to get sum of series 1 – 2 + 3 – 4 + . . . + n in C program. In this tutorial, I’ll show you how to do it in easy way in C program. Here is a simple code for it:

`#include <stdio.h>`

int main()
{
int n,i;
int s=0;

``` printf("Enter the value of n of the series: "); scanf("%d",&n);```

``` printf("Sum of the series: ");```

``` for (i =1; i <= n; i++) { s=s+i*pow(-1,i+1); if(i>=n) printf("%d = %d ",i,s); else if(i%2==0) printf("%d + ",i); else printf("%d - ",i); }```

``` return 0; }```

Output:
``` Enter the value of n of the series: 10 Sum of the series: 1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + 9 - 10 = -5 ```

In above code, I have tried to show number, plus sign, result and in a word equation  by iterating from 2 to n using for loop by incrementing 2 and as well as summing up the series in the iteration.

In this tutorial, I have shown how to get sum of series 1 – 2 + 3 – 4 + . . . + n in C Program. Hope you have enjoyed the tutorial. If you want to get updated, like the facebook page http://www.facebook.com/freetechtrainer and stay connected.