#include <bits/stdc++.h>
using namespace std;
int n, m, a, b, c;
void e() {
  puts("IMPOSSIBLE");
  exit(0);
}
char s[111][111];
int main() {
  scanf("%d%d%d%d%d", &n, &m, &a, &b, &c);
  if ((n * m) % 2) e();
  if (n % 2) a -= m / 2;
  if (m % 2) b -= n / 2;
  if (a < 0 || b < 0) e();
  for (int i = 0; i < n; i++)
    for (int j = 0; j < m; j++) s[i][j] = (i / 2 % 2 == j / 2 % 2) ? 'a' : 'b';
  c -= (n / 2) * (m / 2);
  for (int i = 0; i < n - n % 2; i += 2)
    for (int j = 0; j < m - m % 2; j += 2)
      if (c < 0) {
        if (a > 1)
          a -= 2, c++, s[i][j] = s[i][j + 1] += 2;
        else if (b > 1)
          b -= 2, c++, s[i][j] = s[i + 1][j] += 2;
        else
          e();
      }
  for (int i = 0; i < n; i++)
    for (int j = 0; j < m; j++) printf("%c%s", s[i][j], j == m - 1 ? "\n" : "");
  return 0;
}
