from itertools import product

ways = [(1, 0), (-1, 0), (0, 1), (0, -1)]

x_a, y_a, x_b, y_b, x_c, y_c = map(int, input().split())

ans = 0
for (i_a, j_a), (i_b, j_b), (i_c, j_c) in product(ways, repeat=3):
    X_A, Y_A = x_a + i_a, y_a + j_a
    X_B, Y_B = x_b + i_b, y_b + j_b
    X_C, Y_C = x_c + i_c, y_c + j_c
    
    ans = max(
        ans,
        abs(((X_A - X_C) * (Y_B - Y_C) - (Y_A - Y_C) * (X_B - X_C)) / 2)
    )

print(ans)