inpu = list(map(int,input().rstrip().split(' ')))
BegiNum = 0
Begi = inpu[0]
Meat = inpu[1]
while(inpu[2] + 1 < inpu[3] and Begi > 0 and Meat - inpu[2] > 0):
    BegiNum = BegiNum + 1
    Begi = Begi - 1
    Meat = Meat - inpu[2]
    inpu[3] = inpu[3] - inpu[2] - 1
print(BegiNum)