#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

const int SIGMA = 300;

int main() {
  int N, L, K;
  cin >> N >> L >> K;
  
  string S;
  cin >> S;

  vector<int> count(SIGMA);
  for (const auto c : S) {
    count[c]++;
  }

  vector<string> answer(N, string(L, '?'));
  vector<int> pos(N);
  int l = 0;
  for (int let = 0; let < SIGMA && l != K - 1; let++) {
    if (count[let] == 0) {
      continue;
    }

    int len = K - 1 - l + 1;
    int old_count = count[let];

    int total = len * (L - pos[K - 1]);
    int times = min(L - pos[K - 1], count[let] / len);

    for (int i = l; i < K; i++) {
      for (int j = 0; j < times; j++) {
        answer[i][pos[i]++] = let;
        count[let]--;
      }
    }
    for (int i = 0; i < old_count % len; i++) {
      if (pos[l + i] < L) {
        answer[l + i][pos[l + i]++] = let;
        count[let]--;
      }
    }

    if (pos[K - 1] == L) {
      break;
    }
    if (old_count % len != 0) {
      l += old_count % len;
    }
  }

  for (int let = 0; let < SIGMA; let++) {
    while (count[let] > 0 && pos[K - 1] < L) {
      answer[K - 1][pos[K - 1]++] = let;
      count[let]--;
    }
  }

  for (int let = 0, idx = 0; let < SIGMA; let++) {
    while (count[let] > 0) {
      if (pos[idx] < L) {
        answer[idx][pos[idx]++] = let;
        count[let]--;
      }
      (idx += 1) %= N;
    }
  }

  for (const auto& s : answer) {
    cout << s << "\n";
  }

  return 0;
}