#include<bits/stdc++.h>
using namespace std;
int n,maxbr=0,br1=0;
int br[10];
string s,s1="";
int main()
{
    freopen("password.in","r",stdin);
    freopen("password.out","w",stdout);
    cin>>n;
    cin>>s;
    for(int i=0;i<n;i++)
    {
        br[s[i]-'0']++;
    }
    for(int i=0;i<10;i++)
    {
        if(br[i]>maxbr){maxbr=br[i];br1=0;}
        if(br[i]==maxbr)br1++;
    }
    cout<<br1<<endl;
    for(int i=0;i<10;i++)
    {
        if(br[i]==maxbr)
        {
            for(int j=0;j<maxbr;j++)
            {
                cout<<i;
            }
            cout<<endl;
        }
    }
return 0;
}