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

#include <cstdio>
inline int getInt(){ int s; scanf("%d", &s); return s; }

#include <set>

using namespace std;

int f(int a){
  int ret = 0;
  while(a){
    ret |= 1 << (a % 10);
    a /= 10;
  }
  return ret;
}

int main(){
  const int n = getInt();
  int a = 0;
  REP(i,n) a |= 1 << getInt();
  vector<bool> isPrime(5000000 + 1, true);

  int low = 1;
  int cur = 0;

  int ans = -1;
  for(int i = 2; i <= 5000000; i++){
    if(isPrime[i]){
      cur |= f(i);
      if(cur & ~a){
        cur = 0;
        low = i + 1;
      }

      for(int j = i + i; j <= 5000000; j += i){
        isPrime[j] = false;
      }
    }

    if(cur == a){
      ans = max(ans, i - low);
    }
  }

  printf("%d\n", ans);

  return 0;
}