#include <bits/stdc++.h>
using namespace std;
const int inf_int = 1e9 + 100;
const long long inf_ll = 1e18;
const double pi = 3.1415926535898;
template <class T1, class T2>
std::ostream &operator<<(std::ostream &out, const std::pair<T1, T2> &rhs) {
  out << "( " << rhs.first << " , " << rhs.second << " )";
  return out;
}
template <typename A, typename B>
string to_string(pair<A, B> p);
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);
string to_string(const string &s) { return '"' + s + '"'; }
string to_string(const char *s) { return to_string((string)s); }
string to_string(bool b) { return (b ? "true" : "false"); }
string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}
template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
bool debug = 0;
const int MAXN = 1000 + 100;
const int LOG = 21;
const int mod = 1e9 + 7;
const int MX = (2e7 + 100);
int lcp[MAXN][MAXN];
string s;
long long dp[MAXN][MAXN];
long long suf[MAXN][MAXN];
void solve() {
  int n, m;
  long long k;
  cin >> n >> m >> k;
  cin >> s;
  vector<pair<int, int> > all;
  for (int i = n - 1; i >= 0; --i) {
    lcp[i][i] = n - i;
    for (int j = n - 1; j >= 0; --j) {
      if (s[i] == s[j] && i != j) lcp[i][j] = 1 + lcp[i + 1][j + 1];
    }
  }
  for (int i = 0; i < n; ++i) {
    for (int j = i; j < n; ++j) {
      all.push_back({i, j});
    }
  }
  sort(all.begin(), all.end(), [](pair<int, int> a, pair<int, int> b) -> bool {
    int len1 = a.second - a.first + 1;
    int len2 = b.second - b.first + 1;
    int lc = lcp[a.first][b.first];
    if (lc < min(len1, len2)) {
      return s[a.first + lc] < s[b.first + lc];
    }
    return len1 < len2;
  });
  42;
  int l_bin = 0, r_bin = (int(all.size())) - 1;
  int ans = -1;
  while (l_bin <= r_bin) {
    int mid = (l_bin + r_bin) >> 1;
    int l = all[mid].first, r = all[mid].second;
    int len = r - l + 1;
    memset(dp, 0, sizeof dp);
    memset(suf, 0, sizeof suf);
    dp[0][n] = 1;
    const long long MX = 2e18;
    for (int i = 1; i <= m; ++i) {
      for (int j = n; j >= 0; --j) {
        suf[i][j] = dp[i - 1][j] + suf[i][j + 1];
        suf[i][j] = min(suf[i][j], MX);
      }
      for (int j = n - 1; j >= 0; --j) {
        int lc = min(lcp[j][l], len);
        if (lc == len) {
          dp[i][j] = suf[i][j + lc];
        } else if (j + lc < n && s[j + lc] >= s[l + lc]) {
          dp[i][j] = suf[i][j + lc + 1];
        }
        42;
        42;
      }
    }
    long long res = dp[m][0];
    42;
    if (res >= k) {
      ans = mid;
      l_bin = mid + 1;
    } else {
      r_bin = mid - 1;
    }
  }
  assert(ans != -1);
  42;
  42;
  cout << s.substr(all[ans].first, all[ans].second - all[ans].first + 1)
       << "\n";
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cout.setf(ios::fixed);
  cout.precision(15);
  int t = 1;
  while (t--) solve();
  42;
}
