#include <bits/stdc++.h>
int n, m, a, b, c;
int ans[110][110];
int find(int i, int j) {
  for (int k = 1; k <= 10; k++) {
    if (k != ans[i][j - 1] && k != ans[i - 1][j] && k != ans[i + 1][j - 1] &&
        k != ans[i - 1][j + 1])
      return k;
  }
}
void output() {
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) printf("%c", ans[i][j] + 'a' - 1);
    printf("\n");
  }
}
int getans(int n, int m, int a, int b, int c) {
  if (b < 0) return 0;
  int test = c * 4 + (a / 2) * 4 + (b / 2) * 4;
  if (test < n * m) return 0;
  for (int i = 1; i < n; i += 2) {
    for (int j = 1; j < m; j += 2) {
      if (c > 0) {
        ans[i][j] = ans[i][j + 1] = ans[i + 1][j] = ans[i + 1][j + 1] =
            find(i, j);
        c--;
      } else if (a >= 2) {
        ans[i][j] = ans[i][j + 1] = find(i, j);
        ans[i + 1][j] = ans[i + 1][j + 1] = find(i + 1, j);
        a -= 2;
      } else {
        ans[i][j] = ans[i + 1][j] = find(i, j);
        ans[i][j + 1] = ans[i + 1][j + 1] = find(i, j + 1);
        b -= 2;
      }
    }
  }
  return 1;
}
int main() {
  while (scanf("%d %d %d %d %d", &n, &m, &a, &b, &c) != EOF) {
    memset(ans, 0, sizeof(ans));
    if (n % 2 == 1 && m % 2 == 1)
      printf("IMPOSSIBLE\n");
    else if (n % 2 == 0 && m % 2 == 1) {
      if (b * 2 < n)
        printf("IMPOSSIBLE\n");
      else {
        int found = 1;
        b -= n / 2;
        found = getans(n, m - 1, a, b, c);
        for (int i = 1; i < n; i += 2) ans[i][m] = ans[i + 1][m] = find(i, m);
        if (found == 0)
          printf("IMPOSSIBLE\n");
        else
          output();
      }
    } else if (n % 2 == 1 && m % 2 == 0) {
      if (a * 2 < m)
        printf("IMPOSSIBLE\n");
      else {
        int found = 1;
        a -= m / 2;
        found = getans(n - 1, m, a, b, c);
        for (int i = 1; i < m; i += 2) ans[n][i] = ans[n][i + 1] = find(n, i);
        if (found == 0)
          printf("IMPOSSIBLE\n");
        else
          output();
      }
    } else {
      int found = getans(n, m, a, b, c);
      if (found == 0)
        printf("IMPOSSIBLE\n");
      else
        output();
    }
  }
  return 0;
}
