#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<tuple>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define Per(i,sta,n) for(int i=n-1;i>=sta;i--)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
typedef long double ld;
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;

vector<int> prime_list(int l,int r){//[l,r]に含まれる素数表
    vector<int> li(r+1,1);
    for(int i=2;i<=r;i++){
        if (!li[i]) continue;
        for(int j=2*i;j<=r;j+=i){
            li[j]=0;
        }
    }
    vector<int> res={};
    for(int i=max(2,l);i<=r;i++){
        if (li[i]) res.push_back(i);
    }
    return res;
}

int n,x;
int a[11];

int check(int x){
    int res=0;
    while(x>0){
        int a=x%10;
        res|=(1 << a);
        x/=10;
    }
    return res;
}

void solve(){
    cin >> n;
    if (n==10){
        cout << 4999999 << endl;
        return;
    }
    rep(i,n){
        cin >> a[i];
        x|=(1 << a[i]);
    }
    //cout << bitset<10>(x) << endl;
    vector<int> prime=prime_list(0,5000000);
    int m=prime.size();
    //cout << m << endl;
    int l=0,r=0,ans=-1,s=0;
    while (true){
        int t=check(prime[r]);
        //if (r<=10)cout << bitset<10>(t) << endl;
        if((t&x)!=t) {
            if (r<=10) {
                //cout << prime[l] << " " << prime[r] << endl;
                //cout << bitset<10>(s) << endl;
            }
            if (s==x) {
                if (l>=1) ans=max(ans,prime[r]-prime[l-1]-2);
                else ans=max(ans,prime[r]-2);
            }
            l=r+1;
            s=0;
        }
        else s|=t;
        r++;
        if (r==m+1) break;
    }
    cout << ans << endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(50);
    solve();
}