def main():
    a, b, c, d = map(int, input().split(' '))

    vege = 0
    meat = 0
    st = d
    while  vege < a and meat + c <= b and st - vege * (c + 1):
        vege += 1
        meat = c * vege
        st -= vege + meat
    print(vege)

if __name__ =='__main__':
    main()