#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

vector<bool> psieve(int n) {
  vector<bool> pr(n);
  for (int i = 2; i < n; i++)
    pr[i] = true;
  for (int i = 2; i * i < n; i++) {
    if (!pr[i]) continue;
    for (int j = i * i; j < n; j += i)
      pr[j] = false;
  }
  return pr;
}

int calc(int x) {
  int mask = 0;
  while (x) {
    mask |= 1<<(x % 10);
    x /= 10;
  }
  return mask;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;
  int valid = 0;
  for (int i = 0; i < n; i++) {
    int x;
    cin >> x;
    valid |= 1<<x;
  }
    
  int ret = -1;
  auto pr = psieve(5000000+1);
  for (int i = 1; i <= 5000000; ) {
    int j = i;
    int acc = 0;
    while (j <= 5000000) {
      bool ck = true;
      if (pr[j]) {
        acc |= calc(j);
        if ((valid | acc) != valid)
          ck = false;
      }
      if (!ck)
        break;
      if (acc == valid)
        ret = max(ret, j - i);
      ++j;
    }
    i = j + 1;
  }

  cout << ret << endl;
  
  return 0;
}