#include <cstdio>
#include <iostream>
#include <vector>

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,j) FOR(i,0,j)

typedef long long ll;

std::vector<int> primes;
bool isPrime[5000101];
int xs[348518];
int N, A[10];

int main(){
    std::fill(isPrime, isPrime+5000101, true);
    std::fill(&xs[0], &xs[0]+348518, 0);

    primes.push_back(0);
    primes.push_back(2);
    xs[1] = 0x4;
    for(int i=4;i<=5000100;i+=2){isPrime[i] = false;}

    int length = 2;
    for(ll i=3;i<=5000100;i+=2){
        if(isPrime[i]){
            primes.push_back(i);
            int x = i;
            while(x > 0){xs[length] |= 1 << (x % 10); x /= 10;}
            length += 1;
                    
            for(ll j=i*i;j<=5000100ll;j+=i){
                isPrime[j] = false;
            }
        }
    }

    scanf("%d", &N);
    int restricted = 0;
    REP(i, N){int a; scanf("%d", &a); restricted |= 1 << a;}

    int res = -1;
    for(int i=1,j=1;i<348514;){
        int y = 0;
        while(j < 348514 && (~restricted & xs[j]) == 0){
            y |= xs[j];
            j += 1;
        }

        if(y == restricted){
            res = std::max(res, std::min(primes[j],5000001)-primes[i-1]-2);
        }
        
        i = j+1;
        j = i;
    }

    printf("%d\n", res);
}