char = input().split(" ")
a = int(char[0])
b = int(char[1])
c = int(char[2])
d = int(char[3])

vegi_list = [0]
for vegi in range(d + 1):
    meat = d - vegi
    if meat >= vegi * c and vegi + meat <= d:
        vegi_list.append(vegi)

print(max(vegi_list))