import java.util.*;
public class Practicer {
public static void main(String[] args) {
Scanner cin = new Scanner(System.in);
while(cin.hasNext()){
int a = cin.nextInt();
int b = cin.nextInt();
int c = cin.nextInt();
double s = ((a+b+c)/2);
//double price = s*(s-a)*(s-b)*(s-c);
System.out.printf("%.0f",s*(s-a)*(s-b)*(s-c));
//注意是printf，不是println
}
}
}