A, B, X, Y = map(int, input().split())
flg = 0
Y_baseX = X * B / A
if Y_baseX > Y:
    Y_baseX = 0
    flg = 1
X_baseY = Y * A / B
if X_baseY > X:
    X_baseY = 0
    flg = 2

if flg == 1:
    print(X_baseY + Y)
elif flg == 2:
    print(Y_baseX + X)
elif Y_baseX + X > X_baseY + Y:
    print(Y_baseX + X)
else:
    print(X_baseY + Y)