A, B, C, D = input().split()
A, B, C, D = int(A), int(B), int(C), int(D)
res, su = 0, 0
for i in range(1, D):
    if i % 2 != 0:
        meet = C
        vegi = 0
        su += meet
        B -= C
    else:
        res += 1
        su += 1
        A -= 1
    if su > D or A < 0 or B < 0:
        break
print(res)