#!/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)
ds.sort(reverse=True)
res = 0
for i in xrange(n):
    k = z / ds[i]
    res += k
    z -= ds[i] * k
    if z == 0:
        break
if z > 0:
    res = -1
print res