#include <bits/stdc++.h>
using namespace std;
vector<string> solve(int n, int m, int a, int b, int c) {
  vector<string> res(n, string(m, ' '));
  if (n % 2 == 1 && m % 2 == 1) return vector<string>(1, "IMPOSSIBLE");
  if (m % 2 == 1) {
    for (int i = 0; i < n; i += 2) {
      if (b > 0) {
        res[i][m - 1] = res[i + 1][m - 1] = 'x' + (i % 4);
        b--;
      } else
        return vector<string>(1, "IMPOSSIBLE");
    }
  }
  if (n % 2 == 1) {
    for (int i = 0; i < m; i += 2) {
      if (a > 0) {
        res[n - 1][i] = res[n - 1][i + 1] = 'x' + (i % 4);
        a--;
      } else
        return vector<string>(1, "IMPOSSIBLE");
    }
  }
  for (int i = 0; i + 1 < n; i += 2) {
    for (int j = 0; j + 1 < m; j += 2) {
      if (c > 0) {
        res[i][j] = res[i + 1][j] = res[i][j + 1] = res[i + 1][j + 1] =
            'a' + (i + j) % 4;
        c--;
      } else if (b > 1) {
        res[i][j] = res[i + 1][j] = 'a' + (i + j) % 4;
        res[i][j + 1] = res[i + 1][j + 1] = 'a' + (i + j) % 4 + 1;
        b -= 2;
      } else if (a > 1) {
        res[i][j] = res[i][j + 1] = 'a' + (i + j) % 4;
        res[i + 1][j] = res[i + 1][j + 1] = 'a' + (i + j) % 4 + 1;
        a -= 2;
      } else {
        return vector<string>(1, "IMPOSSIBLE");
      }
    }
  }
  return res;
}
int main() {
  int n, m, a, b, c;
  while (cin >> n >> m >> a >> b >> c) {
    vector<string> vs = solve(n, m, a, b, c);
    for (int i = 0; i < vs.size(); i++) cout << vs[i] << endl;
  }
}
