// editor1
#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";
        
    }
    return 0;
}