#include <bits/stdc++.h>
using namespace std;
string s;
int n, cnt[300];
vector<vector<int> > ans;
int main() {
  cin >> n;
  cin >> s;
  int nos = 0;
  for (int i = 0; i < n; i++) cnt[s[i]]++;
  for (int i = 0; i < 300; i++) {
    if (cnt[i] % 2 == 1) {
      ans.push_back(vector<int>(1, i));
      cnt[i]--;
      nos++;
    }
  }
  if (nos == 0) {
    string res;
    for (int i = 0; i < 300; i++) {
      for (int j = 0; j < cnt[i] / 2; j++) res.push_back(i);
    }
    cout << 1 << endl;
    cout << res;
    reverse(res.begin(), res.end());
    cout << res << endl;
    return 0;
  }
  int sum = 0, q = 0;
  for (int i = 0; i < 300; i++) sum += cnt[i];
  while (sum % (2 * nos) != 0) {
    sum -= 2;
    nos += 2;
    for (q; q < 300;)
      if (cnt[q] >= 2) {
        cnt[q] -= 2;
        ans.push_back(vector<int>(1, q));
        ans.push_back(vector<int>(1, q));
        break;
      } else
        q++;
  }
  int add = sum / nos;
  int idx = 0;
  for (int i = 0; i < 300;) {
    while (ans[idx].size() != 1 + add && cnt[i] != 0) {
      ans[idx].push_back(i);
      cnt[i]--;
    }
    if (ans[idx].size() == 1 + add) idx++;
    if (cnt[i] == 0) i++;
  }
  cout << nos << endl;
  for (int i = 0; i < nos; i++) {
    map<int, int> mct;
    for (int j = 0; j < ans[i].size(); j++) {
      mct[ans[i][j]]++;
    }
    char mid;
    string out;
    for (auto it : mct) {
      if (it.second % 2 == 1) mid = it.first;
      for (int j = 0; j < it.second / 2; j++) out.push_back(it.first);
    }
    cout << out;
    cout << mid;
    reverse(out.begin(), out.end());
    cout << out << " ";
  }
  cout << endl;
  return 0;
}
