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#include <bits/stdc++.h>
#ifndef ONLINE_JUDGE
# pragma GCC diagnostic warning "-Wall"
# pragma GCC diagnostic warning "-Wextra"
# pragma GCC diagnostic warning "-Wformat=2"
# pragma GCC diagnostic warning "-Wnull-dereference"
# pragma GCC diagnostic warning "-Wduplicated-branches"
# pragma GCC diagnostic warning "-Wduplicated-cond"
# pragma GCC diagnostic warning "-Wfloat-equal"
# pragma GCC diagnostic warning "-Wshadow"
# pragma GCC diagnostic warning "-Wconversion"
# pragma GCC diagnostic warning "-Wlogical-op"
# pragma GCC diagnostic warning "-Wvector-operation-performance"
# pragma GCC diagnostic warning "-Wdisabled-optimization"
# pragma GCC diagnostic warning "-Wunsafe-loop-optimizations"
# pragma GCC diagnostic warning "-Wdouble-promotion"
#endif
#pragma GCC target "arch=ivybridge", "tune=ivybridge"
#if defined(ONLINE_JUDGE) || !defined(__OPTIMIZE__)
# pragma GCC optimize "Ofast", "inline", "unroll-loops", "ipa-pta", "no-rtti", \
  "no-exceptions", "nothrow-opt", "strict-enums", "stdarg-opt", "tracer"
# pragma GCC target "inline-all-stringops"
#endif
#define rangeof(c) (c).begin(), (c).end()

using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
using ld = long double;

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;
  cin >> n;
  string s;
  cin >> s;
  int zeroc = 0, onec = 0;
  for(char c: s) {
    if(c == '0') {
      zeroc++;
    } else if(c == '1') {
      onec++;
    }
  }
  
  zeroc -= n;
  onec -= 2 * n;
  if(zeroc < 0 || onec < 0) {
    cout << "NIE\n";
    return 0;
  }
  
  /*set<pair<int, int>> bases;
  for(char i = 'a'; i <= 'z'; i++) {
    int zeroc = 0;
    int onec = 0;
    for(int j = 0; j < 5; j++) {
      if(i & (1u << j)) {
        onec++;
      } else {
        zeroc++;
      }
    }
    bases.insert({zeroc, onec});
    cout << i << " " << zeroc << " " << onec << endl;
  }
  
  for(auto [a, b]: bases) {
    cout << a << " " << b << "\n";
  }
  
  int k = 35;
  vector<vector<bool>> is(k, vector<bool>(k, false));
  is[0][0] = true;
  
  for(int y = 0; y < k; y++) {
    for(int x = 0; x < k; x++) {
      for(auto [a, b]: bases) {
        if(x - a < 0 || y - b < 0) continue;
        if(is[x - a][y - b]) {
          is[x][y] = true;
          break;
        }
      }
      cout << is[x][y];
    }
    cout << "\n";
  }*/
  
  auto is_ok = [&](int zeroc, int onec) {
    return zeroc >= onec / 4 && onec >= zeroc / 4;
  };
  
  if(!is_ok(zeroc, onec)) {
    cout << "NIE\n";
    return 0;
  }
  
  int const alphac = 'z' - 'a' + 1;
  
  vector<pair<int, int>> letters_bits(alphac, {0, 0});
  for(char c = 'a'; c <= 'z'; c++) {
    for(int j = 0; j < 5; j++) {
      if(c & (1u << j)) {
        letters_bits[c - 'a'].second++;
      } else {
        letters_bits[c - 'a'].first++;
      }
    }
  }
  
  int seed = 69;
  for(int i = 0; i < n; i++) {
    for(char c_before = 'a'; c_before <= 'z'; c_before++) {
      int c = (2137 * seed + 421 + c_before - 'a') % alphac;
      if(is_ok(zeroc - letters_bits[c].first, onec - letters_bits[c].second)) {
        cout << (char) (c + 'a');
        zeroc -= letters_bits[c].first;
        onec -= letters_bits[c].second;
        seed = c;
        break;
      }
    }
  }
  assert(zeroc == 0 && onec == 0);
  cout << "\n";
}