package main

import (
	"fmt"
	"math"
)

var PRIME = SieveOfEratosthenes(5000000)
var A = make([]bool, 10)

func SieveOfEratosthenes(max int) []int {
	isNotPrime := make([]bool, max+1)
	isNotPrime[0] = true
	isNotPrime[1] = true
	for i := 2; i <= int(math.Sqrt(float64(max))); i++ {
		if isNotPrime[i] {
			continue
		}
		for j := i * i; j <= max; j += i {
			isNotPrime[j] = true
		}
	}
	prime := make([]int, 0, max/2)
	for i, b := range isNotPrime {
		if !b {
			prime = append(prime, i)
		}
	}
	return prime
}

func addNum(count []int, n int) {
	for n > 0 {
		count[n%10]++
		n /= 10
	}
}
func ok(A []bool, n int) bool {
	count := make([]int, 10)
	addNum(count, n)
	for i := 0; i < 10; i++ {
		if !A[i] && count[i] > 0 {
			return false
		}
	}
	return true
}
func AllOK(A []bool, count []int) bool {
	for i := 0; i < 10; i++ {
		if !A[i] && count[i] > 0 {
			return false
		}
		if A[i] && count[i] == 0 {
			return false
		}
	}
	return true
}

func main() {
	var N, tmp int
	ans := -1
	fmt.Scan(&N)
	if N == 10 {
		fmt.Println(4999999)
		return
	}
	for i := 0; i < N; i++ {
		fmt.Scan(&tmp)
		A[tmp] = true
	}

	for i := 0; i < len(PRIME); i++ {
		if !ok(A, PRIME[i]) {
			continue
		}
		var min, max int
		if i == 0 {
			min = 1
		} else {
			min = PRIME[i-1] + 1
		}
		var j int
		for j = i; j < len(PRIME); j++ {
			if !ok(A, PRIME[j]) {
				break
			}
			if j+1 >= len(PRIME) {
				max = 5000000
			} else {
				max = PRIME[j+1] - 1
			}
		}
		count := make([]int, 10)
		for k := i; k < j; k++ {
			addNum(count, PRIME[k])
		}
		if !AllOK(A, count) {
			continue
		}
		if ans < max-min {
			ans = max - min
		}
	}
	fmt.Println(ans)
}