/* -*- coding: utf-8 -*-
 *
 * 3623.cc:  No.3623 2-Letter Shiritori 2 - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int N = 26;
const int NN = N * N;

/* typedef */

/* global variables */

int as[NN];

/* subroutines */

void rec(int i, int &k) {
  as[k++] = i * N + i;
  if (i + 1 < N) {
    as[k++] = i * N + (i + 1);
    rec(i + 1, k);
    as[k++] = (i + 1) * N + i;
    for (int j = i + 2; j < N; j++) {
      as[k++] = i * N + j;
      as[k++] = j * N + i;
    }
  }
}

/* main */

int main() {
  int k = 0;
  rec(0, k);
  //printf(" k=%d\n", k);

  for (int i = 0; i < NN; i++) {
    int c0 = as[i] / N, c1 = as[i] % N;
    printf("%c%c\n", 'A' + c0, 'A' + c1);
  }
  
  return 0;
}