A, B, C, D = map(int, input().split())

if D <= C or B < C:
    print(0)
else:
    ans = 0
    emax = 0
    for i in range(D):
        ans += 1
        A -= 1
        B -= C
        emax += (1 + C)
        if A == 0 or B == 0:
            break
        elif emax > D:
            ans -= 1
            break

    print(ans)