condition = list(input().split())

vegitable = int(condition[0])
origin_meet = int(condition[1])
rate = int(condition[2])
origin_all = int(condition[3])

if vegitable * rate <= origin_meet:
    i = vegitable
else:
    for i in range(vegitable):
        meet = (i+1) * rate
        if (meet > origin_meet):
            break
        all = (i+1) + meet
        if (all > origin_all):
            break

print(i)