#include <bits/stdc++.h>
using namespace std;
int n, m, a, b, c;
int g[105][105];
int main() {
  scanf("%d%d%d%d%d", &n, &m, &a, &b, &c);
  if (n % 2 + m % 2 == 2) {
    printf("IMPOSSIBLE\n");
    return 0;
  }
  int cnt = 1, tn, tm;
  tn = n;
  tm = m;
  if (n % 2 == 1) {
    for (int i = 0; i < m; i += 2) {
      g[n - 1][i] = g[n - 1][i + 1] = cnt;
      cnt++;
      a--;
    }
    tn--;
  }
  if (m % 2 == 1) {
    for (int i = 0; i < n; i += 2) {
      g[i][m - 1] = g[i + 1][m - 1] = cnt;
      cnt++;
      b--;
    }
    tm--;
  }
  if (a < 0 || b < 0) {
    printf("IMPOSSIBLE\n");
    return 0;
  }
  a -= a % 2;
  b -= b % 2;
  if ((a / 2 + b / 2 + c) * 4 < tn * tm) {
    printf("IMPOSSIBLE\n");
    return 0;
  }
  for (int i = 0; i < tn; i += 2)
    for (int j = 0; j < tm; j += 2) {
      if (c > 0) {
        g[i][j] = g[i + 1][j] = g[i][j + 1] = g[i + 1][j + 1] = cnt;
        cnt++;
        c--;
      } else if (b > 0) {
        g[i][j] = g[i + 1][j] = cnt;
        cnt++;
        b--;
        g[i][j + 1] = g[i + 1][j + 1] = cnt;
        cnt++;
        b--;
      } else {
        g[i][j] = g[i][j + 1] = cnt;
        cnt++;
        a--;
        g[i + 1][j] = g[i + 1][j + 1] = cnt;
        cnt++;
        a--;
      }
    }
  int v[17];
  for (int i = 0; i < n; i++)
    for (int j = 0; j < m; j++)
      if (g[i][j] > 0) {
        memset(v, 0, sizeof(v));
        for (int x = -1; x <= 2; x++)
          for (int y = -1; y <= 2; y++)
            if (i + x >= 0 && i + x < n && j + y >= 0 && j + y < m &&
                g[i + x][j + y] <= 0) {
              v[-g[i + x][j + y]] = 1;
            }
        int col;
        for (int k = 0; k < 17; k++)
          if (v[k] == 0) {
            col = k;
            break;
          }
        for (int x = 0; x < 2; x++)
          for (int y = 0; y < 2; y++)
            if (x + y > 0 && g[i + x][j + y] == g[i][j]) {
              g[i + x][j + y] = -col;
            }
        g[i][j] = -col;
      }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) printf("%c", -g[i][j] + 'a');
    printf("\n");
  }
}
