#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

int main()
{
    freopen("password.in", "r", stdin);
    freopen("password.out", "w", stdout);
    int n;
    string s;
    vector<char> v;
    cin>>n>>s;
    int maxLen=0, len=1;
    char curNum=s[0];
    for(int i=1; i<n; i++)
    {

        if(curNum==s[i])
        {
            len++;
        }
        else
        {
            if(len>maxLen)
            {
                maxLen=len;
                v.clear();
                v.push_back(curNum);
            }
            else if(len==maxLen)
            {
                v.push_back(curNum);
            }
            curNum=s[i];
            len=1;
        }
    }
    if(len>maxLen)
    {
        maxLen=len;
        v.clear();
        v.push_back(curNum);
    }
    else if(len==maxLen)
    {
        v.push_back(curNum);
    }
    cout<<v.size()<<endl;
    for(char c : v)
    {
        for(int i=1; i<=maxLen; i++)
            cout<<c;
        cout<<endl;
    }
    return 0;
}