#include <iostream>
#include <algorithm>
using namespace std;
const int N=5000001;
int c[N];
int main()
{
    vector<int> primes;
    vector<int> v;
    for(int i=2;i<N;++i) if (!c[i]) {
        primes.push_back(i);
        int x=0;
        for(int t=i;t>0;t/=10) x|=1<<(t%10);
        v.push_back(x);
        for(int j=i+i;j<N;j+=i) c[j]=1;
    }

    int n;
    while (cin>>n) {
        int a=0;
        for(int i=0;i<n;++i) { int t; cin>>t; a|=1<<t; }
        int s=0, e=0, x=v[s];
        int res=-1;
        while (s<v.size() and e<v.size()) {
            if ((x|v[e]|a)>a) {
                if (x==a and s<e) {
                    int L=primes[e]-1;
                    int K=!!s*primes[s-1]+1;
                    res=max(res, L-K);
                }
                s=e+1;
                e=s;
                x=v[e];
            }
            else {
                x|=v[e];
                ++e;
            }
            if (x==a) {
                int L=e<primes.size()?primes[e]-1:5000000;
                int K=!!s*primes[s-1]+1;
                res=max(res, L-K);
            }
        }
        cout<<res<<endl;
    }
}