#include <bits/stdc++.h>
using namespace std;
template <typename T>
void maxtt(T& t1, T t2) {
  t1 = max(t1, t2);
}
template <typename T>
void mintt(T& t1, T t2) {
  t1 = min(t1, t2);
}
bool debug = 0;
int n, m, k;
int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
string direc = "URDL";
const long long MOD2 = (long long)1000000007 * (long long)1000000007;
long long ln, lk, lm;
void etp(bool f = 0) {
  puts(f ? "YES" : "NO");
  exit(0);
}
void addmod(int& x, int y, int mod = 1000000007) {
  x += y;
  if (x >= mod) x -= mod;
  if (x < 0) x += mod;
  assert(x >= 0 && x < mod);
}
void et(int x = -1) {
  printf("%d\n", x);
  exit(0);
}
long long fastPow(long long x, long long y, int mod = 1000000007) {
  long long ans = 1;
  while (y > 0) {
    if (y & 1) ans = (x * ans) % mod;
    x = x * x % mod;
    y >>= 1;
  }
  return ans;
}
long long gcd1(long long x, long long y) { return y ? gcd1(y, x % y) : x; }
char s[1035];
int lcp[1035][1035], cnt;
pair<int, int> a[1035 * 1035];
bool cmp(pair<int, int> a, pair<int, int> b) {
  int t = lcp[a.first][b.first];
  if (t >= a.second - a.first + 1 || t >= b.second - b.first + 1) {
    return a.second - a.first < b.second - b.first;
  }
  return s[a.first + t] < s[b.first + t];
}
bool ck(int mid) {
  vector<vector<long long>> dp(n + 5, vector<long long>(n + 5, 0));
  vector<vector<long long>> d(n + 5, vector<long long>(n + 5, 0));
  d[n + 1][0] = 1;
  int len = a[mid].second - a[mid].first + 1;
  for (int i = n; i; i--) {
    int t = min(lcp[i][a[mid].first], len);
    if (t == len || s[i + t] > s[a[mid].first + t]) {
      for (int(j) = 0; (j) < (int)(m); (j)++) dp[i][j + 1] = d[i + t + 1][j];
    }
    for (int(j) = 0; (j) < (int)(m + 1); (j)++) {
      d[i][j] = min(d[i + 1][j] + dp[i][j], lk);
    }
  }
  return dp[1][m] >= lk;
}
void fmain(int tid) {
  scanf("%d%d%lld", &n, &m, &lk);
  scanf("%s", s + 1);
  for (int i = n; i; i--) {
    for (int j = n; j; j--) {
      lcp[i][j] = s[i] == s[j] ? lcp[i + 1][j + 1] + 1 : 0;
    }
  }
  for (int(i) = 1; (i) <= (int)(n); (i)++)
    for (int j = i; j <= n; j++) a[++cnt] = {i, j};
  sort(a + 1, a + 1 + cnt, cmp);
  int l = 1, r = cnt;
  while (l + 1 < r) {
    int mid = (l + r) / 2;
    if (ck(mid))
      l = mid;
    else
      r = mid;
  }
  for (int i = a[r].first; i <= a[r].second; i++) {
    printf("%c", s[i]);
  }
  puts("");
}
int main() {
  int t = 1;
  for (int(i) = 1; (i) <= (int)(t); (i)++) {
    fmain(i);
  }
  return 0;
}
