#include <bits/stdc++.h>
using namespace std;
const int N = 100 + 5;
int n, m, a, b, c, x[N][N];
char y[N][N];
void closeIt() {
  cout << "IMPOSSIBLE";
  exit(0);
}
int main() {
  cin >> n >> m >> a >> b >> c;
  if (n & 1 && m & 1) closeIt();
  if (n & 1) {
    if ((a -= m / 2) < 0) closeIt();
    for (int i = 0; i < m; i += 2) x[n - 1][i] = 1;
  }
  if (m & 1) {
    if ((b -= n / 2) < 0) closeIt();
    for (int i = 0; i < n; i += 2) x[i][m - 1] = 2;
  }
  for (int i = 0; i < n - 1; i += 2)
    for (int j = 0; j < m - 1; j += 2)
      if (a > 1) {
        x[i][j] = x[i + 1][j] = 1;
        a -= 2;
      } else if (b > 1) {
        x[i][j] = x[i][j + 1] = 2;
        b -= 2;
      } else if (c) {
        x[i][j] = 3;
        c--;
      } else
        closeIt();
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++)
      if (x[i][j] == 1)
        y[i][j] = y[i][j + 1] = 'a' + (i + j) % 26;
      else if (x[i][j] == 2)
        y[i][j] = y[i + 1][j] = 'a' + (i + j) % 26;
      else if (x[i][j] == 3)
        y[i][j] = y[i + 1][j] = y[i][j + 1] = y[i + 1][j + 1] =
            'a' + (i + j) % 26;
    cout << y[i] << endl;
  }
}
