#include <bits/stdc++.h>
using namespace std;
template <typename T>
void UpdateMax(T& a, T b) {
  if (a < b) a = b;
}
template <typename T>
void UpdateMin(T& a, T b) {
  if (a > b) a = b;
}
template <typename T>
inline void read(T& x) {
  x = 0;
  char c = getchar();
  int flag = 1;
  while (!isdigit(c)) {
    if (c == '-') flag = -1;
    c = getchar();
  }
  while (isdigit(c)) {
    x = x * 10 + c - '0';
    c = getchar();
  }
  x *= flag;
}
template <typename T>
void Unique(vector<T>& vec) {
  sort(vec.begin(), vec.end());
  vec.erase(unique(vec.begin(), vec.end()), vec.end());
}
template <typename T>
void Relabel(vector<T>& vec, T& value) {
  value = lower_bound(vec.begin(), vec.end(), value) - vec.begin() + 1;
}
template <typename T, typename V>
void Print(const pair<T, V>& x) {
  cout << x.first << " @ " << x.second << " | ";
}
template <typename T>
void Print(const T& x) {
  cout << x << " ";
}
template <typename T>
void Pcon(const T& x) {
  cout << "\nsize: " << x.size() << endl;
  for (const auto& item : x) Print(item);
}
std::vector<int> LABS;
template <typename T>
void Print(const T* x, int offset, int loop) {
  for (int i = 0; i <= loop; i++) {
    cout << "[";
    for (int item : LABS) cout << item - offset << ",";
    cout << i - offset << "]:";
    cout << x[i] << " ";
  }
}
template <typename T, typename... Args>
void Print(const T* f, int offset, int loop, Args... args) {
  for (int i = 0; i <= loop; i++) {
    LABS.push_back(i);
    Print(f[i], offset, args...);
    cout << endl;
    LABS.pop_back();
  }
}
template <typename T, typename V>
bool Has(T& cluster, const V& item) {
  return cluster.find(item) != cluster.end();
}
int Logn(long long x) {
  int cnt = 0;
  while (x) {
    ++cnt;
    x >>= 1;
  }
  return cnt;
}
const int MOD = 1e9 + 7;
const int N = 2e5 + 5;
const int dir[4][2] = {{-1, 0}, {0, -1}, {1, 0}, {1, 0}};
struct Edg {
  Edg() {}
  Edg(int x, int y, int z) : x(x), y(y), z(z) {}
  int x, y, z;
  friend bool operator<(const Edg& lhs, const Edg& rhs) {
    return lhs.z < rhs.z;
  }
} edg[N];
bool vis[N], used[N];
clock_t start_time;
int t, n, m, a, b, c;
int f[N];
vector<int> G[N];
inline void SetClock() { start_time = clock(); }
bool TimeOut(size_t ms) {
  if (1000 * (clock() - start_time) >= ms * ((clock_t)1000)) return true;
  return false;
}
inline pair<int, int> DeSerialize(int c) { return {(c) / m, (c) % m}; }
template <typename T, typename V>
inline void Add(T& v, const V& delta) {
  v += delta;
  if (v >= MOD) v -= MOD;
}
template <typename T, typename V>
inline void Dec(T& v, const V& delta) {
  v -= delta;
  if (v < 0) v += MOD;
}
char A[105][105];
char nextChar(int x, int y) {
  std::unordered_set<char> color;
  if (x) {
    color.emplace(A[x - 1][y]);
    color.emplace(A[x - 1][y + 1]);
  }
  if (y) {
    color.emplace(A[x][y - 1]);
    color.emplace(A[x + 1][y - 1]);
  }
  color.emplace(A[x + 1][y - 1]);
  for (char nextC = 'a'; nextC <= 'z'; ++nextC) {
    if (color.find(nextC) == color.end()) {
      return nextC;
    }
  }
  return 'a';
}
void fill(int n, int m) {
  for (int i = 0; i < n; i += 2) {
    for (int j = 0; j < m; j += 2) {
      if (c) {
        A[i][j] = A[i][j + 1] = A[i + 1][j] = A[i + 1][j + 1] = nextChar(i, j);
        --c;
      } else if (a >= 2) {
        A[i][j] = A[i][j + 1] = nextChar(i, j);
        A[i + 1][j] = A[i + 1][j + 1] = nextChar(i + 1, j);
        a -= 2;
      } else {
        A[i][j] = A[i + 1][j] = nextChar(i, j);
        A[i][j + 1] = A[i + 1][j + 1] = nextChar(i, j + 1);
        b -= 2;
      }
    }
  }
}
int main() {
  srand(time(0));
  SetClock();
  cin.sync_with_stdio(false);
  cin >> n >> m >> a >> b >> c;
  if ((n * m) & 1) {
    cout << "IMPOSSIBLE" << endl;
    return 0;
  }
  if ((n & 1) == 0 && (m & 1) == 0) {
    if (c * 4 + a / 2 * 4 + b / 2 * 4 < n * m) {
      cout << "IMPOSSIBLE" << endl;
      return 0;
    }
    fill(n, m);
  } else if (n & 1) {
    if (a * 2 < m) {
      cout << "IMPOSSIBLE" << endl;
      return 0;
    }
    a -= m / 2;
    if (c * 4 + a / 2 * 4 + b / 2 * 4 < (n - 1) * m) {
      cout << "IMPOSSIBLE" << endl;
      return 0;
    }
    fill(n - 1, m);
    for (int j = 0; j < m; j += 2) {
      A[n - 1][j] = A[n - 1][j + 1] = nextChar(n - 1, j);
    }
  } else {
    if (b * 2 < n) {
      cout << "IMPOSSIBLE" << endl;
      return 0;
    }
    b -= n / 2;
    if (c * 4 + a / 2 * 4 + b / 2 * 4 < n * (m - 1)) {
      cout << "IMPOSSIBLE" << endl;
      return 0;
    }
    fill(n, m - 1);
    for (int i = 0; i < n; i += 2) {
      A[i][m - 1] = A[i + 1][m - 1] = nextChar(i, m - 1);
    }
  }
  for (int(i) = 0; (i) < (n); ++(i)) {
    for (int(j) = 0; (j) < (m); ++(j)) {
      cout << A[i][j];
    }
    cout << endl;
  }
}
