#include<cstdio>
#include<vector>


using namespace std;


#define L_MAX 5000000


class prime_t
{
public:
	int x;
	int c[10];
	prime_t(int x)
	{
		int i;
		for(i=0;i<10;i++) c[i]=0;
		this->x=x;
		for(;x;x/=10)
		{
			c[x%10]=1;
		}
	}
};


vector<prime_t> prime;


void init(void)
{
	int i, j;

	prime.clear();
	prime.reserve(L_MAX/4);
	prime.push_back(prime_t(0));
	prime.push_back(prime_t(2));
	for(i=3;i<=L_MAX;i+=2)
	{
		for(j=3;j*j<=i;j+=2)
		{
			if(i%j==0) break;
		}
		if(j*j>i)
		{
			prime.push_back(prime_t(i));
		}
	}
	prime.push_back(prime_t(L_MAX+1));
}


int max_u(int& m, int v)
{
	if(m<v)
	{
		m=v;
		return 1;
	}
	return 0;
}


int main(void)
{
	int n, i;
	vector<int> a, b, c, f;
	int ps, pe, max, d, k, l, ok, ng;

	init();
	while(scanf("%d", &n)==1)
	{
		a.resize(n);
		f.clear();
		f.resize(10);
		c.clear();
		c.resize(10);

		for(i=0;i<n;i++)
		{
			scanf("%d", &a[i]);
			f[a[i]]=1;
		}

		ok=ng=0;
		max=-1;
		ps=1;
		for(pe=1;pe+1<prime.size();pe++)
		{
			for(i=0;i<10;i++)
			{
				d=prime[pe].c[i];
				if(d==0) continue;

				if(c[i]==0)
				{
					if(f[i]) ok++;
					else ng++;
				}
				c[i]++;
			}
			if(ok==n)
			{
				for(;ps<=pe;ps++)
				{
					if(ng==0) break;
					for(i=0;i<10;i++)
					{
						d=prime[ps].c[i];
						if(d==0) continue;

						c[i]--;
						if(c[i]==0)
						{
							if(f[i]) ok--;
							else ng--;
						}
					}
				}
			}

			if(ok==n && ng==0)
			{
				k=prime[ps-1].x+1;
				l=prime[pe+1].x-1;
				if(max_u(max, l-k))
				{
//					printf("l=%d k=%d max=%d\n", l, k, max);
				}
			}
		}
		printf("%d\n", max);
	}

	return 0;
}