How to Add Integer using File in C.

#include <stdio.h>

int main()

{

    int a,i,sum=0;

    FILE *fp,*fp1; ///file type pointer declared

    fp=fopen("input.txt","r"); ///scan file from a text file which you have to create and save data

    for(i=0; i<5; i++)

    {

        fscanf(fp,"%d",&a);

        sum+=a;   ///add all the elements

    }

    fclose(fp);

    fp1=fopen("output.txt","w"); ///print in text file you don't have to Create this file

    fprintf(fp1,"The Sum is :%d",sum);

    fclose(fp1);

    return 0;

}