#include<iostream>
using namespace std;

int main(){
    double m,v;
    if(!(cin>>m>>v)) return 0;
    
    if(m<0 ||v0){
        cout<<"Invalid Input"<<endl;
    }else{
        double ke=0.5*m*v*v;
        cout<<ke<<endl;
    }
    return 0;
    
}