#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:268435456")
using namespace std;
template <typename T>
inline T abs(T a) {
  return ((a < 0) ? -a : a);
}
template <typename T>
inline T sqr(T a) {
  return a * a;
}
template <class T>
T gcd(T a, T b) {
  return a ? gcd(b % a, a) : b;
}
template <class T>
T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
template <class T>
T sign(T a) {
  return a > 0 ? 1 : (a < 0 ? -1 : 0);
}
const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, 1, 0, -1};
const int dxK[] = {-1, -1, 0, 1, 1, 1, 0, -1};
const int dyK[] = {0, 1, 1, 1, 0, -1, -1, -1};
const int dxKn[] = {-2, -1, 1, 2, 2, 1, -1, -2};
const int dyKn[] = {1, 2, 2, 1, -1, -2, -2, -1};
const int N = int(1e2) + 9;
const int M = int(3e3) + 9;
const int LOGN = 22;
const int SQN = 350;
const int MOD = int(1e9) + 7;
const int INF = 1e9 + 100;
const long long INF64 = 2e18;
const long double PI = 3.1415926535897932384626433832795;
const long double EPS = 1e-9;
int n, m, a, b, c;
char res[N][N];
void solve() {
  memset(res, '.', sizeof res);
  cin >> n >> m >> a >> b >> c;
  if (n & 1) {
    if ((m & 1) || m / 2 > a) {
      cout << "IMPOSSIBLE";
      return;
    }
    for (int i = 0; i < (int)(m / 2); ++i) {
      if (i & 1)
        res[0][i * 2] = res[0][i * 2 + 1] = 'a', --a;
      else
        res[0][i * 2] = res[0][i * 2 + 1] = 'b', --a;
    }
  } else {
    if (m & 1) {
      if (n / 2 > b) {
        cout << "IMPOSSIBLE";
        return;
      }
      for (int i = 0; i < (int)(n / 2); ++i) {
        if (i & 1)
          res[i * 2][0] = res[i * 2 + 1][0] = 'a', --b;
        else
          res[i * 2][0] = res[i * 2 + 1][0] = 'b', --b;
      }
    }
  }
  for (int i = 0; i < (int)(n); ++i)
    for (int j = 0; j < (int)(m); ++j) {
      if (res[i][j] == '.') {
        if (c > 0) {
          set<char> ok;
          for (char cur = 'a'; cur <= 'z'; ++cur) ok.insert(cur);
          for (int di = -1; di <= 2; ++di)
            for (int dj = -1; dj <= 2; ++dj)
              if ((0 <= i + di && i + di < n && 0 <= j + dj && j + dj < m))
                ok.erase(res[i + di][j + dj]);
          res[i][j] = res[i + 1][j] = res[i][j + 1] = res[i + 1][j + 1] =
              *ok.begin();
          --c;
        } else if (a > 1) {
          set<char> ok;
          for (char cur = 'a'; cur <= 'z'; ++cur) ok.insert(cur);
          for (int di = -1; di <= 2; ++di)
            for (int dj = -1; dj <= 2; ++dj)
              if ((0 <= i + di && i + di < n && 0 <= j + dj && j + dj < m))
                ok.erase(res[i + di][j + dj]);
          res[i][j] = res[i][j + 1] = *ok.begin();
          res[i + 1][j] = res[i + 1][j + 1] = *ok.rbegin();
          a -= 2;
        } else if (b > 1) {
          set<char> ok;
          for (char cur = 'a'; cur <= 'z'; ++cur) ok.insert(cur);
          for (int di = -1; di <= 2; ++di)
            for (int dj = -1; dj <= 2; ++dj)
              if ((0 <= i + di && i + di < n && 0 <= j + dj && j + dj < m))
                ok.erase(res[i + di][j + dj]);
          res[i][j] = res[i + 1][j] = *ok.begin();
          res[i][j + 1] = res[i + 1][j + 1] = *ok.rbegin();
          b -= 2;
        }
      }
    }
  for (int i = 0; i < (int)(n); ++i)
    for (int j = 0; j < (int)(m); ++j)
      if (res[i][j] == '.') {
        cout << "IMPOSSIBLE";
        return;
      }
  for (int i = 0; i < (int)(n); ++i) {
    for (int j = 0; j < (int)(m); ++j) cout << res[i][j];
    cout << endl;
  }
}
int main() {
  srand(time(NULL));
  cout << setprecision(10) << fixed;
  cerr << setprecision(10) << fixed;
  solve();
  return 0;
}
