#include<iostream>
using namespace std;
class calculator {
    public:
    double calculator(int a,int b ,int type)
    {
        if (a<=0||b<=0)
        {
            cout<<"Invalid input"<<endl;
            
            return 0;
        }
        switch (type)
        {
            case 1:cout<<a+b; break;
            case 2:cout<<a-b; break;
            case 3:cout<<a*b; break;
            case 4:if (b==0) cout<<"Division by zero";
            else cout<<(double)a/b;
            break;
            default:cout<<"Invalid input";
        }
        return 0;
    }
    switch (type){
        case1:cout<<a+b:break;
        case2:cout<<a-b;break;
        case3:cout<<a*b;break;
        case4:if(b==0) cout<<"Division by zero";
        else cout<<a/b;
        break;
        default:cout<<"Invalid input";
    }
    return 0;
};
}
int main(){
    unt type;
    double a,b;
    cin>>type>>a>>b;
    calculator calc;
    calc.calculate(a,b,type);
    return 0;
}
}