#include <iostream>
#include <fstream>

using namespace std;

double maxelem(istream& f);

int main() {
    ifstream f("input.txt");
    if (!f.is_open()) {
        cerr << "Cannot open an input file." << endl;
        return (-1);
    }
    
    double y = maxelem(f);    
    f.close();
    
    cout << "Maximal element: " << y << endl;
    return 0;
}

double maxelem(istream& f) {
    double y = -1e30;  // -infinity
    double x;
    while (f >> x) {
        if (x > y)
           y = x;
    }
    return y;
}