#include <iostream>
#include <cmath>
#include <set>
using namespace std;
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))

const int LIM = 5000000;

bool isprime[LIM+1];
void  sieve_of_atkin(int N) {
    int n;
    int sqrtN = (int)sqrt((double)N);
    for(int z = 1; z <= 5; z += 4){
        for(int y = z; y <= sqrtN; y += 6){
            for(int x = 1; x <= sqrtN && (n = 4*x*x+y*y) <= N; ++x)      isprime[n] = !isprime[n];
            for(int x = y+1; x <= sqrtN && (n = 3*x*x-y*y) <= N; x += 2) isprime[n] = !isprime[n];
        }
    }
    for(int z = 2; z <= 4; z += 2){
        for(int y = z; y <= sqrtN; y += 6){
            for(int x = 1; x <= sqrtN && (n = 3*x*x+y*y) <= N; x += 2)   isprime[n] = !isprime[n];
            for(int x = y+1; x <= sqrtN && (n = 3*x*x-y*y) <= N; x += 2) isprime[n] = !isprime[n];
        }
    }
    for(int y = 3; y <= sqrtN; y += 6){
        for(int z = 1; z <= 2; ++z){
            for(int x = z; x <= sqrtN && (n = 4*x*x+y*y) <= N; x += 3)   isprime[n] = !isprime[n];
        }
    }
    for(int n = 5; n <= sqrtN; ++n)
        if(isprime[n]) for(int k = n*n; k <= N; k+=n*n) isprime[k] = false;
    isprime[2] = isprime[3] = true;
}

int main(){
    int N, n;
    set<int> setN;
    cin >> N;
    REP(i,N){
        cin >> n;
        setN.insert(n);
    }
    sieve_of_atkin(LIM);
    set<int> setK;
    int low = 1;
    int maxv = -1;
    for(int i = 1; i <= LIM; i++){
        if(!isprime[i]) continue;
        int j = i;
        bool flag = true;
        set<int> add;
        while(j){
            if(setN.count(j%10)){
                add.insert(j%10);
                j /= 10;
            } else {
                flag = false;
                break;
            }
        }
        if(!flag){
            if(low && setK.size() == N){
                maxv = max(maxv, (i-1)-low);
#ifdef _DEBUG
                if(maxv == (i-1)-low){
                    cout << low << ":" << i-1 << ":" << ((i-1)-low) << endl;
                    for(int j = low; j <= i-1; j++){
                        if(isprime[j]) cout << j << " ";
                    }
                    cout << endl;
                }
#endif
            }
            low = i+1;
            setK.clear();
        } else {
            setK.insert(add.begin(), add.end());
        }
    }
    if(setK.size() == N){
        maxv = max(maxv, LIM-low);
#ifdef _DEBUG
        if(maxv == (LIM-low)){
        	cout << low << ":" << LIM << ":" << (LIM-low) << endl;
            for(int j = low; j <= LIM; j++){
                if(isprime[j]) cout << j << " ";
            }
            cout << endl;
        }
#endif
    }
    cout << maxv << endl;
    return 0;
}