//package testjava;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		System.out.println("Nhap vao canh a: ");
		int a = input.nextInt();
		System.out.println("Nhap vao canh b: ");
		int b = input.nextInt();
		System.out.println("Nhap vao canh c: ");
		int c = input.nextInt();
		float p = (a + b + c) / 2;
		if (((a + b) > c) && ((b + c) > a) && ((a + c) > b)) {
			System.out.println("Dien tich tam giac la:"
					+ (Math.sqrt(p * (p - a) * (p - b) * (p - c))));
		} else
			System.out.println("Khong phai la tam giac");
	}
}