#include <iostream>
using namespace std;
int x1, x2, y1, y2, ans;
int D[2200][2200];
int main()
{
for (int t = 1; t <= 3; t++)
{
cin >> x1 >> y1 >> x2 >> y2;
for (int x = x1; x < x2; x++)
{
for (int y = y1; y < y2; y++)
{
D[x + 1000][y + 1000] = t;
}
}
}
for (int x = 0; x <= 2000; x++)
{
for (int y = 0; y <= 2000; y++)
{
if (D[x][y] == 1 || D[x][y] == 2)
ans++;
}
}
cout << ans;
}