#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = (ll)(1e+9) + 7;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
typedef long double ld;
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;
typedef pair<ld, ld> LDP;
int c[10];
bool a[10];
int s() {
	int res = 0;
	rep(i, 10) {
		if (a[i] && c[i] == 0)res = max(res, 1);
		if (!a[i] && c[i] > 0)res = max(res, 2);
	}
	return res;
}
const int key = 5000000;
bool isp[key+1];
void init() {
	fill(isp+2, isp + key+1, true);
	Rep1(i,2, key) {
		if (!isp[i])continue;
		for (int j = 2 * i; j <= key; j += i) {
			isp[j] = false;
		}
	}
}
void add(int x) {
	while (x) {
		c[x % 10]++; x /= 10;
	}
}
void red(int x) {
	while (x) {
		c[x % 10]--; x /= 10;
	}
}
int main(){
	init();
	int n; cin >> n;
	rep(i, n) {
		int t; cin >> t;
		a[t] = true;
	}
	int le = 1; int out = -1;
	rep1(i, key) {
		if(isp[i])add(i);
		while (s() == 2) {
			if (isp[le])red(le);
			le++;
		}
		if (s() == 0)out = max(out, i - le);
	}
	cout << out << endl;
	return 0;
}