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#if defined(EMBE_DEBUG) && !defined(NDEBUG)
#include "embe-debug.hpp"
#else
#define LOG_INDENT(...) do {} while (false)
#define LOG(...) do {} while (false)
#define DUMP(...) do {} while (false)
#endif

#include <cassert>
#include <iostream>
#include <optional>
#include <string>
using namespace std;

namespace {

optional<string> solve(int n, int zeros, int ones)
{
  assert(ones + zeros == 8 * n);
  if (zeros < 2 * n || ones < 3 * n) return {};
  string res;
  res.reserve(n);
  while (n > 0) {
    int o = ones / n;
    assert(o >= 3);
    assert(o <= 6);
    char c = 'a' + (1 << (o - 2)) - 2;
    assert(c >= 'a' && c <= 'z');
    assert(__builtin_popcount(c) == o);
    res.push_back(c);
    ones -= o;
    zeros -= 8 - o;
    --n;
  }
  assert(ones == 0);
  assert(zeros == 0);
  return res;
}

}

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

  int n;
  cin >> n;

  int zeros = 0;
  int ones = 0;

  for (int i = 0; i < 8 * n; ++i) {
    char c;
    cin >> c;
    if (c == '0') ++zeros;
    else assert(c == '1'), ++ones;
  }

  auto res = solve(n, zeros, ones);
  if (!res) cout << "NIE" << endl;
  else cout << *res << endl;

  return 0;
}