// Reads three numbers from the file specified by the user, sums the 
// numbers, and writes the sum to another file specified by the user.
// mixes console I/O and file I/O
// Walt Savitch
// 03/14/00

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

using std::ifstream; using std::ofstream; using std::endl;
using std::cin; using std::cout; using std::string;

int main() {

    ifstream fin;
    ofstream fout;

    string inFileName;
    string outFileName;

    cout << "Enter the input file name: ";
    cin >> inFileName;

    cout << "Enter the output file name: ";
    cin >> outFileName;

    cout << "I will read numbers from the file "
         << inFileName
         << "and place the sum in the file "
         << outFileName << endl;

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

    fout.open(outFileName.c_str());
    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 three numbers in"
         << inFileName << "is " 
	 << first + second + third
         << endl;

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

    cout << "End of Program.\n";
}