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

int main(){
  int N;
  cin >> N;
  vector<char> A(N);
  for(int i=0;i<N;i++) cin >> A[i];
  int M = 5000000;
  vector<bool> Prime(M+1,true);
  Prime[0] = Prime[1] = false;
  for(int i=2;i<=M;i++){
    if(Prime[i]){
      for(int j=2*i;j<=M;j+=i){
        Prime[j] = false;
      }
    }
  }
  int ans = -1;
  int L=1,R=1;
  vector<bool> used(N,false);
  bool can = false;
  for(int i=2;i<=M;i++){
    if(!Prime[i]){
      R++;
      if(can) ans = max(ans,R-L);
      
    }
    else{
      string S = to_string(i);
      bool ok = true;
      for(int j=0;j<S.size();j++){
        bool exist = false;
        for(int k=0;k<N;k++){
          if(S[j] == A[k]){
            exist = true;
            used[k] = true;
          }
        }
        if(!exist) ok = false;
      }
      if(ok){
        bool clear = true;
        for(int j=0;j<N;j++) if(!used[j]) clear = false;
        if(clear) can = true;
        R++;
        if(can) ans = max(ans,R-L);
      }
      else{
        can = false;
        for(int j=0;j<N;j++) used[j] = false;
        L = i+1;
        R = i;
      }
    }
  }
  cout << ans << endl;
}