#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <cstring>

typedef long long ll;
using namespace std;

#define mod 1000000007
#define INF 1000000000
#define LLINF 2000000000000000000LL

#define MAX_L 5000000
#define SIZE 1000000

vector<int> pnum;

const int MAX_P = 5000000;
bool prime[MAX_P+1];
void primen(void){
    for(int i=2;i<=MAX_P;i++)
        prime[i]=true;
    
    for(int i=2;i*i<=MAX_P;i++)
        if(prime[i])
            for(int j=i;i*j<=MAX_P;j++)
                prime[i*j]=false;
    
}

int main(){
    int n,k,A,ans=-1,a,f;
    int m[10]={0},m_in[10]={0};
    
    scanf("%d",&n);
    
    primen();
    
    pnum.push_back(0);
    
    for(int i=2;i<=MAX_L;i++){
        if(prime[i]==true){
            pnum.push_back(i);
        }
    }
    
    pnum.push_back(5000001);

    
    for(int i=0;i<n;i++){
        scanf("%d",&A);
        
        m_in[A]=1;
    }
    
    k=1;
    
    for(int l=1;l<pnum.size();l++){
        
        
        while(1){
            bool f = false;
            
            for(int i=0;i<10;i++){
                if(m_in[i]==0 && m[i]>0)
                    f = true;
            }
        
            if(f){
                a = pnum[k];
                
                while(a){
                    m[a%10]--;
                    a/=10;
                }
                
                k++;
            }else{
                break;
            }
            
        }
        
        bool f = true;
        
        for(int i=0;i<10;i++){
            if(m_in[i]>0 && m[i]==0)
                f = false;
        }
        
        if(f){
            ans = max(ans,(pnum[l]-1)-(pnum[k-1]+1));
        }
        
        a = pnum[l];
        
        while(a){
            m[a%10]++;
            a/=10;
        }
    }
    
    printf("%d\n",ans);
    
    return 0;
}