/* -*- coding: utf-8 -*-
 *
 * 12.cc: No.12 限定された素数 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_P = 5000000;

/* typedef */

typedef vector<int> vi;

struct DCount {
  int ds[10];
  DCount() { memset(ds, 0, sizeof(ds)); }
  DCount(int _n) {
    memset(ds, 0, sizeof(ds));
    while (_n > 0) {
      ds[_n % 10] = 1;
      _n /= 10;
    }
  }

  void inc(int i) { ds[i]++; }

  void add(const DCount &d) {
    for (int i = 0; i < 10; i++) ds[i] += d.ds[i];
  }

  bool match(const DCount &d) const {
    for (int i = 0; i < 10; i++)
      if (ds[i] == 0 && d.ds[i] > 0) return false;
    return true;
  }

  bool all(const DCount &d) const {
    for (int i = 0; i < 10; i++)
      if ((ds[i] == 0 && d.ds[i] > 0) || (ds[i] > 0 && d.ds[i] == 0))
	return false;
    return true;
  }

  void print() {
    for (int i = 0; i < 10; i++) printf("%d ", ds[i]); putchar('\n');
  }
};

/* global variables */

bool primes[MAX_P + 1];

/* subroutines */

void gen_primes(int maxp, vi &pnums) {
  memset(primes, true, sizeof(primes));
  primes[0] = primes[1] = false;

  int p;
  for (p = 2; p * p <= maxp; p++)
    if (primes[p]) {
      pnums.push_back(p);
      for (int q = p * p; q <= maxp; q += p) primes[q] = false;
    }
  for (; p <= maxp; p++)
    if (primes[p]) pnums.push_back(p);
}

/* main */

int main() {
  int n;
  cin >> n;

  DCount g;
  
  for (int i = 0; i < n; i++) {
    int ai;
    cin >> ai;
    g.inc(ai);
  }
  //g.print();

  vi pnums;
  gen_primes(MAX_P, pnums);
  int pn = pnums.size();

  vector<DCount> dcs;
  for (int i = 0; i < pn; i++) dcs.push_back(DCount(pnums[i]));

  int maxd = -1;
  
  for (int i = 0; i < pn;) {
    while (i < pn && ! g.match(dcs[i])) i++;
    if (i >= pn) break;

    int j = i + 1;
    DCount dc(dcs[i]);
    while (j < pn && g.match(dcs[j])) dc.add(dcs[j++]);

    if (g.all(dc)) {
      int k = (i > 0) ? pnums[i - 1] + 1 : 1;
      int l = (j < pn) ? pnums[j] - 1 : MAX_P;
      int d = l - k;
      if (maxd < d) maxd = d;
    }

    i = j;
  }

  printf("%d\n", maxd);
  return 0;
}