#include<iostream>
#include<cmath>
using namespace std;
class shape{
    protected:
    int t;
    public:
    void display(){
        cin>>t;
    }
    
};
class Area:public shape{
    protected:
    int length;
    int len,width;
    int radius;
    double PI =3.14;
    public:
    void display1(){
        cin>>lenght>>len>>width>>radius;
        if(length<0 && len<0 && width<0 && radius <0){
            cout<<"Invalid input";
            return 0;
        }
        if(t==1){
            cout<<length*length;
        }
        else if(t==2){
            cout<<lenght*width;
        }
        else{
            cout<<radius*radius*PI;
        }
    }
};
int main (){
    Area a;
    a.display;
    a.display1();
    return 0;
}