A, B, C, D = map(int, input().split())
total = 0
res = 0
while total + C + 1 < D and B >= C and A > 0 and B > 0:
    #print(res, total, A, B)
    res += 1
    total += 1 + C
    A -= 1
    B -= C
    #print(res, total, A, B)
print(res)