#include<iostream>
#include<cmath>
using namespace std;
double area(double s){return s<0?-l:s*s}
double area(double l,double w){return(l<0||w<0)?-l:l*w;}
double areaCircle(doubler r){return r<0? l:M_Pl*r*r;}
int main(){
    int t;cin>>t;
    double a,b;
    if(t==l){cin>>a>>;cout<<{area(a,b)==-l?"Invalid input":to_string((int)area(a)));}
        else if(t==2){ciin>>a>>b;cout<<(area(a,b)==-l?"Invalid input"):to_string((int)area(a,b)));}
        else if(t==3){cin>>a;cout<<(areaCircle(a)==-1?"Invalid input"):to_string(areaCircle(a)));}
        else cout<<"Invalid input";
    }