#include <iostream>
int main()
{
    int a,b;
    FILE* f1;
    FILE* f2;
    f1 = fopen("input.dat", "r");
    f2 = fopen("output.dat", "w");
    fscanf(f1, "%d %d", &a, &b);
    fprintf(f2, "%d", a + b);
    return 0;
}

It gives when submitted Crash (access viaolation)...
I have no idea what the problem may be...

you don't need to open any files
use scanf and printf. see FAQ for clarification.

Oh, I have obviosly misunderstood the problem.
Thanks for the help!

import java.util.*;
class Sumar
{
    private int a,b;
    public Sumar(int a,int b)
    {

        this.a=a;
        this.b=b;
    }
    public int sumar()
    {
        return a + b;
    }
     public static void main (String[] args)
    {
        int a,b;
        Scanner in =new Scanner(System.in);
         a=in.nextInt();
         b=in.nextInt();
         Sumar res=new Sumar(a,b);
        System.out.print(res.sumar());

    }
}