#include <iostream>
using namespace std;

double s(double a, double h){
    return a * h / 2;
}

int main(void){
    double a, h;;
    cout << "底辺:";
    cin >> a;
    cout << "高さ:";
    cin >> h;
    cout << "三角形の面積:" << s(a, h) << endl;
    return 0;
}

底辺:高さ:三角形の面積:0