#!/usr/bin/python2
# -*- coding: utf-8 -*-
# †
inf = float('inf')
n = int(raw_input())
ds = map(int, raw_input().split())
x, y = map(int, raw_input().split())
x, y = abs(x), abs(y)
z = max(x, y)

mini = inf

for i in xrange(n):
    for j in xrange(n):
        a, b = ds[i], ds[j]
        # 足りない
        k = z / a
        dif = z - a*k
        assert dif >= 0
        if dif % b == 0:
            res = k + dif/b
            mini = min(mini, res)
        # 行きすぎ
        dif = a*(k+1) - z
        assert dif >= 0
        if dif % b == 0:
            res = k + 1 + dif/b
            mini = min(mini, res)

if mini == inf:
    mini = -1
print mini