#include <iostream>
using namespace std;
int main()
{
	int a,b,c,t;
	cin >> a>>b>>c;
	if(a<b)
	{
		t = a;
		a = b;
		b = t;
	}
	if (b<c)
	{
		t = b;
		b = c;
		c = t;
	}
	if (a<b)
	{
		t = a;
		a = b;
		b = t;
	}
	cout << (a*b+a*c+b*c)*2-a*b;
} 
/**************************************************************
	Problem: 1340
	User: xiaomingze
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/