#include <bits/stdc++.h>
using namespace std;

int main() {
  int N, MX = 5e6;
  cin >> N;
  vector<int> A(10);
  for (int a; cin >> a;) A.at(a)++;

  vector<bool> B(MX + 1, 1);
  B.at(0) = B.at(1) = 0;
  for (long i = 2; i <= MX; i++) if (B.at(i)) for (long j = i * i; j <= MX; j += i) B.at(j) = 0;
  vector<int> P;
  for (int i = 1; i <= MX; i++) if (B.at(i)) P.push_back(i);

  int ans = 0;
  vector<int> cnt(10);
  for (int l = 0, r = 0, mi = 0, mx = 0; r < P.size(); r++) {
    int tmp = P.at(r);
    while (tmp) cnt.at(tmp % 10)++, tmp /= 10;
    for (int i = 0; i < 10; i++) {
      if (!A.at(i) && cnt.at(i)) {
        l = r + 1;
        fill(cnt.begin(), cnt.end(), 0);
        goto next;
      }
    }
    for (int i = 0; i < 10; i++) {
      if (A.at(i) && !cnt.at(i)) {
        goto next;
      }
    }
    mi = ((l - 1 >= 0) ? P.at(l - 1) : 0) + 1;
    mx = ((r + 1 < P.size()) ? P.at(r + 1) : 5e6 + 1) - 1;
    ans = max(ans, mx - mi);
    next:;
  }
  cout << ((ans) ? ans : -1) << "\n";
}