#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define foru(i,from,n) for(int i=from;i<(int)(n);i++)
#define ford(i,from,n) for(int i=(int)(n)-1;i>=0;i--)
#define vi vector<int>
#define pb push_back
#define fi first
#define se second
#define _ << " " <<
using namespace std;

int main() {
    #ifndef LOCAL
        freopen("password.in", "r", stdin);
        freopen("password.out", "w", stdout);
    #endif

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int N;
    cin>>N;
    string pali;
    cin>>pali;
    int digs[10];
    memset(digs,0,sizeof(digs));
    rep(i,N) {
        digs[pali[i]-'0']++;
    }
    int maxdigs=-1;
    rep(i,10) {
        if(maxdigs<digs[i])maxdigs=digs[i];
    }
    int numAns = 0;
    rep(i,10) {
        if(maxdigs==digs[i])numAns++;
    }
    char buf[500000];
    char* p=buf;
    p+=sprintf(p,"%d\n",numAns);
    rep(i,10) {
        if(maxdigs==digs[i]) {
            rep(j,maxdigs)p+=sprintf(p,"%d",i);
            p+=sprintf(p,"\n");
        }
    }
    printf(buf);
    
    return 0;
}