#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, a, b, c;
  cin >> n >> m >> a >> b >> c;
  if (n % 2 == 1 && m % 2 == 1) {
    cout << "IMPOSSIBLE\n";
    return 0;
  }
  char ans[n][m];
  int xoff = 0, yoff = 0;
  if (n % 2 == 1) {
    for (int i = 0; i < m; i += 2) {
      ans[0][i] = ans[0][i + 1] = 'a' + (i / 2) % 2;
      a--;
    }
    xoff = 1;
  }
  if (m % 2 == 1) {
    for (int i = 0; i < n; i += 2) {
      ans[i][0] = ans[i + 1][0] = 'a' + (i / 2) % 2;
      b--;
    }
    yoff = 1;
  }
  if (a < 0 || b < 0) {
    cout << "IMPOSSIBLE\n";
    return 0;
  }
  if (a % 2 == 1) a--;
  if (b % 2 == 1) b--;
  char ch = 'c';
  int cur = a;
  char cu = 'a';
  if (a == 0) {
    if (b == 0) {
      cur = c;
      cu = 'c';
    } else {
      cur = b;
      cu = 'b';
    }
  }
  for (int i = xoff; i < n; i += 2) {
    for (int j = yoff; j < m; j += 2) {
      if (a + b + c <= 0) {
        cout << "IMPOSSIBLE\n";
        return 0;
      }
      if (cu == 'a') {
        ans[i][j] = ans[i][j + 1] = ch;
        ans[i + 1][j] = ans[i + 1][j + 1] = ch + 1;
        cur = cur - 2;
      } else if (cu == 'b') {
        ans[i][j] = ans[i + 1][j] = ch;
        ans[i][j + 1] = ans[i + 1][j + 1] = ch + 1;
        cur = cur - 2;
      } else {
        ans[i][j] = ans[i][j + 1] = ch;
        ans[i + 1][j] = ans[i + 1][j + 1] = ch;
        cur = cur - 1;
      }
      if (cur == 0) {
        if (cu == 'a') {
          a = 0;
          if (b == 0) {
            cur = c;
            cu = 'c';
          } else {
            cur = b;
            cu = 'b';
          }
        } else if (cu == 'b') {
          b = 0;
          cur = c;
          cu = 'c';
        } else
          c = 0;
      }
      if (ch == 'c' || ch == 'e')
        ch = ch == 'c' ? 'e' : 'c';
      else
        ch = ch == 'w' ? 'y' : 'w';
    }
    if (ch == 'w' || ch == 'y')
      ch = 'c';
    else
      ch = 'w';
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) cout << ans[i][j];
    cout << endl;
  }
  cout << endl;
  return 0;
}
