#include <bits/stdc++.h>
using namespace std;
int n, m, a, b, c;
char board[110][110];
bool isgood(int a, int b, int c) {
  if (n % 2 && m % 2) return 0;
  if (n % 2) {
    if (a < m / 2)
      return 0;
    else
      a -= (m / 2);
    if (((n - 1) * m) / 4 > a / 2 + b / 2 + c) return 0;
    return 1;
  } else if (m % 2) {
    if (b < n / 2)
      return 0;
    else
      b -= n / 2;
    if (((m - 1) * n) / 4 > a / 2 + b / 2 + c) return 0;
    return 1;
  } else {
    if ((n * m) / 4 > a / 2 + b / 2 + c) return 0;
    return 1;
  }
}
void fillboard() {
  if (n % 2) {
    for (int i = 1, j = 0; i < m; i += 2, j++)
      if (j % 2)
        board[n][i] = board[n][i + 1] = 'a';
      else
        board[n][i] = board[n][i + 1] = 'b';
    a -= (m / 2);
  }
  if (m % 2) {
    for (int i = 1, j = 0; i < n; i += 2, j++) {
      if (j % 2)
        board[i][m] = board[i + 1][m] = 'a';
      else
        board[i][m] = board[i + 1][m] = 'b';
    }
    b -= (n / 2);
  }
  int h = n - (n % 2), w = m - (m % 2);
  for (int i = 1; i < h; i += 2) {
    for (int j = 1; j < w; j += 2) {
      if (c) {
        if ((i + j) % 4 == 0)
          board[i][j] = board[i + 1][j] = board[i][j + 1] =
              board[i + 1][j + 1] = 'c';
        else
          board[i][j] = board[i + 1][j] = board[i][j + 1] =
              board[i + 1][j + 1] = 'd';
        c--;
      } else if (a > 1) {
        if ((j + 1) % 4 == 0) {
          board[i][j] = board[i][j + 1] = 'e';
          board[i + 1][j] = board[i + 1][j + 1] = 'f';
        } else {
          board[i][j] = board[i][j + 1] = 'f';
          board[i + 1][j] = board[i + 1][j + 1] = 'e';
        }
        a -= 2;
      } else if (b > 1) {
        if ((i + 1) % 4 == 0) {
          board[i][j] = board[i + 1][j] = 'g';
          board[i][j + 1] = board[i + 1][j + 1] = 'h';
        } else {
          board[i][j] = board[i + 1][j] = 'h';
          board[i][j + 1] = board[i + 1][j + 1] = 'g';
        }
        b -= 2;
      }
    }
  }
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) printf("%c", board[i][j]);
    printf("\n");
  }
  exit(0);
}
int main() {
  scanf("%d%d%d%d%d", &n, &m, &a, &b, &c);
  if (isgood(a, b, c))
    fillboard();
  else
    cout << "IMPOSSIBLE" << endl;
  return 0;
}
