#include<iostream>
#include<algorithm>

using namespace std;

int main() {
	int vect[4];
	cin >> vect[0] >> vect[1] >> vect[2] >> vect[3];
	sort(vect, vect + 4);
	cout << vect[0] * vect[1] + vect[2] * vect[3];
	system("pause");
	return 0;
}