#include <bits/stdc++.h>
using namespace std;
int n, m, a, b, c;
char str[100][100];
bool solve() {
  if (a < 0 || b < 0) return false;
  for (int i = 0; i + 1 < n; i += 2)
    for (int j = 0; j + 1 < m; j += 2) {
      int p = (i / 2 + j / 2) & 1;
      if (c >= 1) {
        str[i][j] = str[i][j + 1] = str[i + 1][j] = str[i + 1][j + 1] = 'a' + p;
        c--;
      } else if (a >= 2) {
        str[i][j] = str[i][j + 1] = 'c' + p;
        str[i + 1][j] = str[i + 1][j + 1] = 'e' + p;
        a -= 2;
      } else if (b >= 2) {
        str[i][j] = str[i + 1][j] = 'c' + p;
        str[i][j + 1] = str[i + 1][j + 1] = 'e' + p;
        b -= 2;
      } else
        return false;
    }
  return true;
}
int main() {
  scanf("%d%d%d%d%d", &n, &m, &a, &b, &c);
  if (n % 2 == 1 && m % 2 == 1) {
    printf("IMPOSSIBLE\n");
    return 0;
  }
  if (n % 2 == 1) {
    for (int i = 0; i < m; i += 2) {
      a--;
      str[n - 1][i] = str[n - 1][i + 1] = 'x' + (i / 2 % 2);
    }
  }
  if (m % 2 == 1) {
    for (int i = 0; i < n; i += 2) {
      b--;
      str[i][m - 1] = str[i + 1][m - 1] = 'x' + (i / 2 % 2);
    }
  }
  if (solve()) {
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) printf("%c", str[i][j]);
      printf("\n");
    }
  } else
    printf("IMPOSSIBLE\n");
  return 0;
}
