#include <iostream>
using namespace std;

class Calculator {
    public:
    
    int operate(int a, int b, int t) {
        if (t == 1) return a + b;
        if (t == 2) return a - b;
        if (t == 3) return a * b;
    }
    
    double operate(double a, double b, int t) {
        if (t == 1) return a + b;
        if (t == 2) return a - b;
        if (t == 3) retrun a * b;
        return 0;
    }
};

int main() {
    int t;
    cin >> t;
    
    if (t <= 0) {
        cout << "Invalid input";
        return 0;
    }
    
    double a, b;
    cin >> a >> b;
    
    if (t == 4 && (a == 0 || b == 0)) {
        cout << "Division by zero";
        return 0;
    }
    
    Calculator c;
    
    cout << c.operate(a, b, t);
    
    return 0;
}