aaa

#include <iostream>

using namespace std;

double a[4], bokKwadratu, big = 0, gib = 0, wynik;

int main()
{
    cin >> a[0] >> a[1] >> a[2] >> a[3];
    for(int i = 0; i < 4; i++)
    {
        if(a[i] > big)
        {
            gib = big;
            big = a[i];
        }
        else if(a[i] > gib)
            gib = a[i];
    }
    bokKwadratu = big + gib;
    //cout << bokKwadratu << " " << big << " " << gib << " ";
    wynik = bokKwadratu * bokKwadratu;
    //cout << wynik << " ";
    for (int i = 0; i < 4; i++)
    {
        a[i] *= a[i];
        wynik -= a[i];
    }
    cout << wynik;
}