#include <bits/stdc++.h>
using namespace std;
char buf[105][105];
int main() {
  int n, m, a, b, c;
  cin >> n >> m >> a >> b >> c;
  if ((n & 1) && (m & 1)) {
    puts("IMPOSSIBLE");
    return 0;
  } else if (n & 1) {
    if (a < m / 2) {
      puts("IMPOSSIBLE");
      return 0;
    } else {
      for (int i = 0; i < m / 2; i++) {
        buf[n - 1][2 * i] = buf[n - 1][2 * i + 1] = (i & 1) ? 'a' : 'b';
      }
      a -= m / 2;
    }
  } else if (m & 1) {
    if (b < n / 2) {
      puts("IMPOSSIBLE");
      return 0;
    } else {
      for (int i = 0; i < n / 2; i++) {
        buf[2 * i][m - 1] = buf[2 * i + 1][m - 1] = (i & 1) ? 'a' : 'b';
      }
      b -= n / 2;
    }
  }
  if (4 * c + (a / 2) * 4 + (b / 2) * 4 < 4 * (n / 2) * (m / 2)) {
    puts("IMPOSSIBLE");
    return 0;
  } else {
    for (int i = 0; i + 1 < n; i += 2) {
      for (int j = 0; j + 1 < m; j += 2) {
        if ((i / 2 + j / 2) & 1) {
          if (c) {
            buf[i][j] = buf[i + 1][j] = buf[i][j + 1] = buf[i + 1][j + 1] = 'c';
            c--;
          } else if (a > 1) {
            buf[i][j] = buf[i][j + 1] = 'c';
            buf[i + 1][j] = buf[i + 1][j + 1] = 'd';
            a -= 2;
          } else {
            buf[i][j] = buf[i + 1][j] = 'c';
            buf[i][j + 1] = buf[i + 1][j + 1] = 'd';
            b -= 2;
          }
        } else {
          if (c) {
            buf[i][j] = buf[i + 1][j] = buf[i][j + 1] = buf[i + 1][j + 1] = 'e';
            c--;
          } else if (a > 1) {
            buf[i][j] = buf[i][j + 1] = 'e';
            buf[i + 1][j] = buf[i + 1][j + 1] = 'f';
            a -= 2;
          } else {
            buf[i][j] = buf[i + 1][j] = 'e';
            buf[i][j + 1] = buf[i + 1][j + 1] = 'f';
            b -= 2;
          }
        }
      }
    }
  }
  for (int i = 0; i < n; i++) {
    puts(buf[i]);
  }
  return 0;
}
