// reads three numbers from the file infile.dat, sums the numbers, 
// and writes the sum to the file outfile.dat.
// checks if file is opened successfully
// Walt Savitch 
// 03/14/00

#include <fstream>
#include <iostream>
#include <cstdlib>

using std::ifstream; using std::ofstream; using std::endl;

int main() {
    ifstream fin;
    ofstream fout;

    fin.open("infile.dat");
    if (fin.fail()) {
        cout << "Input file opening failed.\n";
        exit(1);
    }

    fout.open("outfile.dat");
    if (fout.fail()) {
        cout << "Output file opening failed.\n";
        exit(1);
    }

    int first, second, third;
    fin >> first >> second >> third;
    fout << "The sum of the first 3 numbers is " 
	 << first + second + third
	 << endl;

    fin.close();
    fout.close();
}