#include<iostream>
using namespace std;
class Calculator{
    int operate(int a,int b,int type){
        if(type==1)return a+b;
        if(type==2)return a-b;
        if(type==3)return a*b;
        if(type==4){
            if(b==0){
                cout<<"Division by zero";
                exit(0);
            }
            return a/b;
        }
        double operate(double a,double b, int type){
            if(type==1)return a+b;
            if(type==2)return a-b;
            if(type==3)return a*b;
            if(type==4){
                cout<<"Division by zero";
                exit(0);
            }
            return a/b;
        }
        return 0.0;
    }
};
int main()
{
    int t;
    cin>>t;
    if(t<=0||t>4){
        cout<<"Invalid input";
        return 0;
    }
    string a_str,b_str;
    cin>>a_str>>b_str;
    Calculator calc;
    if(a_str.find('.')!=string::npos||b_str.find('.')!=string::npos){
        double a=stod(a_str);
        double b=stod(b_str);
        if(a<0||b<0){
            cout<<"Invalid input";
            return 0;
        }
        cout<<calc.operate(a,b,t);
    }
    return 0;
}