def main():
    import sys
    input = sys.stdin.read().split()
    idx = 0
    n = int(input[idx])
    idx += 1
    d_list = list(map(int, input[idx:idx + n]))
    idx += n
    x = int(input[idx])
    y = int(input[idx + 1])
    D = max(abs(x), abs(y))
    if D == 0:
        print(0)
        return
    
    max_d = max(d_list)
    has_even = any(d % 2 == 0 for d in d_list)
    has_odd = any(d % 2 == 1 for d in d_list)
    mixed = has_even and has_odd
    all_even = has_even and not has_odd
    all_odd = has_odd and not has_even
    
    k_min = (D + max_d - 1) // max_d  # ceil(D / max_d)
    
    # Check up to k_min + 4 to handle cases where the minimal k is near the boundary
    for k in range(k_min, k_min + 4 + 1):
        sum_max = k * max_d
        if sum_max < D:
            continue
        ok = False
        if mixed:
            ok = True
        elif all_even:
            ok = (D % 2 == 0)
        else:  # all_odd
            ok = (k % 2 == D % 2)
        if ok:
            print(k)
            return
    print(-1)

if __name__ == "__main__":
    main()