#include <bits/stdc++.h>
using namespace std;
const int INF = 1 << 30;
const double EPS = 1e-7;
const int MAXN = 100;
const int MAXM = 100;
char ans[MAXN][MAXM];
char type[6] = {'a', 'b', 'c', 'd', 'e', 'f'};
int main() {
  ios::sync_with_stdio(false);
  int n, m, a, b, c;
  cin >> n >> m >> a >> b >> c;
  int blacks = (n * m) / 2;
  if ((m % 2 == n % 2 && m % 2 == 1) || (a + b + c * 2 < blacks)) {
    cout << "IMPOSSIBLE" << endl;
    return 0;
  }
  if ((m % 2 == 1 && b < n / 2) || (n % 2 == 1 && a < m / 2)) {
    cout << "IMPOSSIBLE" << endl;
    return 0;
  }
  bool ok = true;
  if (m % 2 == 1) {
    for (int i = 0; i < n; i += 2) {
      ans[i][m - 1] = type[(1 + i / 2) % 2 + 4];
      ans[i + 1][m - 1] = type[(1 + i / 2) % 2 + 4];
    }
    b -= n / 2;
  }
  if (n % 2 == 1) {
    for (int i = 0; i < m; i += 2) {
      ans[n - 1][i] = type[(1 + i / 2) % 2 + 2];
      ans[n - 1][i + 1] = type[(1 + i / 2) % 2 + 2];
    }
    a -= m / 2;
  }
  for (int i = 0; i < n - n % 2; i += 2)
    for (int j = 0; j < m - m % 2; j += 2) {
      if (c) {
        ans[i][j] = type[(i / 2 + j / 2) % 2];
        ans[i + 1][j] = type[(i / 2 + j / 2) % 2];
        ans[i][j + 1] = type[(i / 2 + j / 2) % 2];
        ans[i + 1][j + 1] = type[(i / 2 + j / 2) % 2];
        c--;
      } else if (a >= 2) {
        ans[i][j] = type[(j / 2 + 1) % 2 + 2];
        ans[i + 1][j] = type[(j / 2) % 2 + 2];
        ans[i][j + 1] = type[(j / 2 + 1) % 2 + 2];
        ans[i + 1][j + 1] = type[(j / 2) % 2 + 2];
        a -= 2;
      } else if (b >= 2) {
        ans[i][j] = type[(i / 2 + 1) % 2 + 4];
        ans[i + 1][j] = type[(i / 2 + 1) % 2 + 4];
        ans[i][j + 1] = type[(i / 2) % 2 + 4];
        ans[i + 1][j + 1] = type[(i / 2) % 2 + 4];
        b -= 2;
      } else {
        ok = false;
        break;
      }
    }
  if (!ok) {
    cout << "IMPOSSIBLE" << endl;
    return 0;
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) cout << ans[i][j];
    cout << endl;
  }
  return 0;
}
