A, B, N, M = gets.split.map(&:to_i)
ac, wa = 0, 10**18
while (ac - wa).abs > 1
    wj = (ac + wa) / 2
    x = A - wj
    y = B - wj
    if (x < 0 ? y < 0 ? false : -x <= y / M : y < 0 ? -y <= x / N : true)
        ac = wj
    else
        wa = wj
    end
end
puts ac