package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)

func Scanner() string {
	sc.Scan()
	return sc.Text()
}

func main() {
	buf := make([]byte, 0)
	sc.Buffer(buf, 100000007)
	sc.Split(bufio.ScanWords)
	inf := 5000000
	n, _ := strconv.Atoi(Scanner())
	a := make([]bool, 10)
	num := 0
	for i := 0; i < n; i++ {
		num, _ = strconv.Atoi(Scanner())
		a[num] = true
	}
	if n == 10 {
		fmt.Println(4999999)
		return
	}
	p := prime(5000000)
	var max, min int
	ans := -1
	for i := 0; i < len(p); i++ {
		if !judge(a, p[i]) {
			continue
		} else {
			if i == 0 {
				min = 1
			} else {
				min = p[i-1] + 1
			}
		}
		for j := i; j < len(p); j++ {
			if !judge(a, p[j]) {
				num = j
				break
			}
			if j+1 >= len(p) {
				max = inf
			} else {
				max = p[j+1] - 1
			}
		}
		count := make([]int, 10)
		for k := i; k < num; k++ {
			add(count, p[k])
		}
		if !judge2(a, count) {
			continue
		}
		ans = big(ans, max-min)
	}
	fmt.Println(ans)
}

func prime(n int) []int {
	notprime := make([]bool, n+1)
	prime := make([]int, 0)
	notprime[0] = true
	notprime[1] = true
	for i := 2; i <= n; i++ {
		if notprime[i] {
			continue
		}
		for j := 2 * i; j <= n; j += i {
			notprime[j] = true
		}
	}

	for i, j := range notprime {
		if !j {
			prime = append(prime, i)
		}
	}
	return prime
}

func judge(a []bool, n int) bool {
	count := make([]int, 10)
	add(count, n)
	for i := 0; i < 10; i++ {
		if !a[i] && count[i] > 0 {
			return false
		}
	}
	return true
}

func judge2(a []bool, count []int) bool {
	for i := 0; i < 10; i++ {
		if !a[i] && count[i] > 0 {
			return false
		} else if a[i] && count[i] == 0 {
			return false
		}
	}
	return true
}

func add(count []int, n int) {
	for n > 0 {
		count[n%10]++
		n /= 10
	}
}

func big(x int, y int) int {
	if x >= y {
		return x
	} else {
		return y
	}
}