// editor3
#include<iostream>
#include<cmath>
using namespace std;
float area(float side){
    if (side<0||side>1000)
     return -1;
    return side*side;
    
}
float area(float lenght, float width){
    if(lenght<0||width<0||lenght>1000||width>1000)
        return -1;
    return lenght*width;
        
    }
float area(double radius){
    if (radius<0||radius>1000)
    return -1;
    return M_PI*radius*radius;
}
int main(){
    int t;
    cin>>t;
switch(t){
    case 1:{
            float side;
            cin>>side;
            float a=area(side);
            if(a<0)
            cout>>"Invalid input";
            else
            cout<<a;
            break;
            
        }
        case 2: {
            float lenght,width;
            cin>>lenght>>width;
            float a=area(lenght,width);
            if(a<0)
            cout<<"invalid input";
            else
            cout<<a;
            break;
        }
        case 3:{
            double radius;
            cin>>radius;
            float a=area(radius);
            if(a<0)
            cout<<"Invalid input";
            else cout<<a;
            break;
        }
        default:
        cout<<"Invalid input";
        
    }
    return 0;
}