#include <bits/stdc++.h>

#define REP(i, x, n) for(int i = x; i < (int)(n); i++)
#define rep(i, n) REP(i, 0, n)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define F first
#define S second
#define mp make_pair

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;

const int MAX = 5000000;

bool isPrime[MAX + 1];

void sieve(int N){
  for(int i = 0; i <= N; i++) {
    isPrime[i] = true;
  }
  
  isPrime[0] = isPrime[1] = false;

  for(int i = 2; i <= N; i++) {
    if(!isPrime[i]) continue;
    for(int j = i + i; j <= N; j += i) {
      isPrime[j] = false;
    }
  }
}

int func(int v) {
  int res = 0;
  while(v) {
    int tmp = v % 10;
    v /= 10;
    res |= (1 << tmp);
  }
  return res;
}

int main() {
  // ios_base::sync_with_stdio(false);
  sieve(MAX);

  int N;
  cin >> N;

  int ok = 0;
  rep(i, N) {
    int A;
    cin >> A;
    ok |= (1 << A);
  }

  int ng = ((1 << 10) - 1) ^ ok;
  int ans = -1;
  int K = -1;
  int flg = 0;
  for(int i = 1; i <= MAX; i++) {
    if(K == -1) K = i;

    if(isPrime[i]) flg |= func(i);
    
    if(flg & ng) {
      K = -1;
      flg = 0;
    }
    else if(flg == ok) {
      ans = max(ans, i - K);
    }
  }

  cout << ans << endl;
  
  return 0;
}