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

class area{
    public:
    double b(double s){
        return s>0?s*s:-1;
    }
    double b(double i,double w){
        return(i>0&&w>0)? i*w : -1;
    }
    double b(int r){
        return r>0 ? M_PI*r*r:-1;
    }
};
int main(){
    int t;
    cin>>t;
    area a;
    double x,y;
    int r;
    ans= -1;
    if(t==1){
        cin>>x;
        x=a.b(x);
    }
    else if(t==2){
        cin>>x>>y;
        ans=a.b(x,y);
    }
    else if(t==3){
        cin>>r;
        ans=a.b(r);
    }
    else ans=-1;
    
    if(ans==-1)
    cout<<"Invalid input";
    else
    cout<<ans;
}