#include<iostream>
#include<cmath>
using namespace std;

class AreaCalculator {
    public :
    int area(int side) {
        if(side < 0) return -1;
        return side * side;
    }
    int area(int length, int width) {
        if (length < 0 || width < 0) return -1;
        return length * width;
    }
    double area(double radius) {
        if (radius < 0) return -1.0;
        return M_PI* radius * radius;
    }
    };
    int main() {
        int t;
        cin >> t;
        
        AreaCalculator calc;
        if (t==1) {
            int side;
        cin>>side;
        if (side < 0) {
            cout<<"Invalid input"<<endl;
        } else {
            cout<<calc.area(side) <<endl;
        }
    } else if (t==2) {
        int l,w;
        cin>>l>>w;
        if(l<0 || w<0) {
            cout<<"Invalid input"<<endl;
        } else  {
            cout<<calc.area(l,w)<<endl;
            
            } else if (t==3) {
                double r;
                cin>> r;
                if(r<0) {
                    cout<<"Invalid input"<<endl;
                } else {
                    cout<<cout<<calc.area(r)<<endl;
                    }
            } else {
                cout<<"Invalid input"<<endl;
            }
            return 0;
        }
            }