using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;
using System.Text;

public class Program
{

    public void Proc()
    {
        int itemCount = int.Parse(Reader.ReadLine());
        char[] items = Reader.ReadLine().Split(' ').Select(a => a[0]).ToArray();
        this.PrimeList = this.GetPrimeList();
        int fromIdx = -1;
        int toIdx = -1;
        int ans = -1;
        Dictionary<char, bool> cnt = new Dictionary<char, bool>();
        items.ToList().ForEach(a=>cnt.Add(a, false));
        for (int i = 0; i < PrimeList.Length; i++) {
            string num = PrimeList[i].ToString();
            if(num.All(a=>cnt.ContainsKey(a))) {
                if (fromIdx < 0) {
                    fromIdx = i;
                }
                toIdx = i;
                num.ToList().ForEach(a => cnt[a] = true);
            } else {
                if (fromIdx >= 0 && cnt.All(a=>a.Value)) {
                    int fromNum = 1;
                    if (fromIdx > 0) {
                        fromNum = PrimeList[fromIdx-1]+1;
                    }
                    int toNum = 5000000;
                    if(toIdx < PrimeList.Length - 1) {
                        toNum = PrimeList[toIdx + 1] - 1;
                    }
                    ans = Math.Max(ans, toNum - fromNum);
                }
                fromIdx = -1;
                toIdx = -1;
                cnt.Keys.ToList().ForEach(a => cnt[a] = false);
            }
        }
        if(toIdx >= 0) {
            int fromNum = 1;
            if (fromIdx>0) {
                fromNum = PrimeList[fromIdx - 1] + 1;
            }
            ans = Math.Max(ans, 5000000 - fromNum);
        }
        Console.WriteLine(ans);
    
    }

    private int[] GetPrimeList() {
        int num = 5000000;
        bool[] flags = new bool[num + 1];

        List<int> ret = new List<int>();
        for (int i = 2; i <= num; i++) {
            if (flags[i]) {
                continue;
            }
            ret.Add(i);
            int max = num / i;
            for (int j = 0; j <= max; j++) {
                flags[i*j] = true;
            }
        }
        return ret.ToArray();

	}

    private int[] PrimeList;

    public class Reader
	{
		private static StringReader sr;
		public static bool IsDebug = false;
		public static string ReadLine()
		{
			if (IsDebug)
			{
				if (sr == null)
				{
					sr = new StringReader(InputText.Trim());
				}
				return sr.ReadLine();
			}
			else
			{
				return Console.ReadLine();
			}
		}
		private static string InputText = @"


5
1 2 3 4 5


";
	}

	public static void Main(string[] args)
	{
#if DEBUG
		Reader.IsDebug = true;
#endif
		Program prg = new Program();
		prg.Proc();
	}
}