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

bool IsPrime(ll num){
    if (num<2) return false;
    else if (num == 2) return true;
    else if (num % 2 == 0) return false;

    long sqrtNum = sqrtf(num);
    for (long i = 3; i <= sqrtNum; i += 2){
        if (num % i == 0){
            return false;}}
    return true;}

int main(){
    int n,i,p=1,j,k,l;
    ll ans;
    cin>>n;
    int a[n];
    ll t[2*n];
    t[1]=1;
    for(i=2;i-2*n;++i)t[i]=t[i-1]*10;
    for(i=0;i-n;++i){cin>>a[i];p*=2;}
    p/=2;
    ll s[256]={},y[256]={};
    int aa=0,bb=0;
    ll max=-1;
    for(i=0;i-p;++i){
         k=i;
         ans=a[0];
         l=a[0]>9?2:1;
         for(j=1;j-n;++j){
             l+=a[j]>9?2:1;
             if(k%2)ans+=a[j]*t[l];
             else{ans*=a[j]>9?100:10;ans+=a[j];}
             k/=2;}
         ll k=0;
         for(j=0;j-aa;++j)if(s[j]==ans){k=1;break;}
         if(!k)for(j=0;j-bb;++j)if(y[j]==ans){k=1;break;}
         if(!k){
             if(IsPrime(ans)){
             s[aa++]=ans;
             max=max>ans?max:ans;}
             else y[bb++]=ans;
         }}
    cout<<max<<"\n";
}