#include <bits/stdc++.h>
char get_char(int x, int y) {
  char start_s = 'c';
  start_s += ((x / 2) % 2) * 6;
  y /= 2;
  start_s += 2 * (y % 3);
  return start_s;
}
int main() {
  int n, m, a, b, c;
  std::cin >> n >> m >> a >> b >> c;
  if ((n * m) % 2 == 1 || n * m > c * 4 + a * 2 + b * 2) {
    std::cout << "IMPOSSIBLE";
    return 0;
  }
  char mas[100][100] = {0};
  int nn = n, mm = m;
  if (n % 2 == 1) {
    if (a < m / 2) {
      std::cout << "IMPOSSIBLE";
      return 0;
    }
    a -= m / 2;
    nn--;
    for (int i = 0; i < m; i += 2) {
      mas[nn][i] = (i / 2) % 2 + 'a';
      mas[nn][i + 1] = (i / 2) % 2 + 'a';
    }
  }
  if (m % 2 == 1) {
    if (b < n / 2) {
      std::cout << "IMPOSSIBLE";
      return 0;
    }
    b -= n / 2;
    mm--;
    for (int i = 0; i < n; i += 2) {
      mas[i][mm] = (i / 2) % 2 + 'a';
      mas[i + 1][mm] = (i / 2) % 2 + 'a';
    }
  }
  for (int i = 0; i < nn; i += 2)
    for (int j = 0; j < mm; j += 2) {
      char s = get_char(i, j);
      if (c > 0) {
        mas[i][j] = s;
        mas[i + 1][j] = s;
        mas[i][j + 1] = s;
        mas[i + 1][j + 1] = s;
        c--;
      } else if (a > 1) {
        mas[i][j] = s;
        mas[i][j + 1] = s;
        mas[i + 1][j] = s + 1;
        mas[i + 1][j + 1] = s + 1;
        a -= 2;
      } else if (b > 1) {
        mas[i][j] = s;
        mas[i + 1][j] = s;
        mas[i][j + 1] = s + 1;
        mas[i + 1][j + 1] = s + 1;
        b -= 2;
      } else {
        std::cout << "IMPOSSIBLE";
        return 0;
      }
    }
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < m; j++) std::cout << mas[i][j];
    if (i != n - 1) std::cout << "\n";
  }
  return 0;
}
