#include <bits/stdc++.h>
using namespace std;
int main(){
  int H, W;
  cin >> H >> W;
  int X;
  cin >> X;
  if (X < H + W - 2 || X % 4 != (H + W - 2) % 4){
    cout << -1 << endl;
  } else {
    bool tr = false;
    if (W % 4 == 3){
      tr = true;
      swap(H, W);
    }
    vector<string> S(H, string(W, '.'));
    for (int i = 0; i < H; i++){
      for (int j = 1; j < W; j += 2){
        S[i][j] = '#';
      }
    }
    X -= H + W - 2;
    S[H - 1][1] = '.';
    for (int i = 3; i < W; i += 2){
      if (X >= (H - 1) * 2){
        if (i < W - 1){
          S[0][i] = '.';
          S[H - 1][i + 2] = '.';
          X -= (H - 1) * 2;
          i += 2;
        }
      } else {
        int a = H - 1 - X / 2;
        S[a][i] = '.';
        X = 0;
      }
    }
    if (X > 0){
      cout << -1 << endl;
    } else {
      if (tr){
        vector<string> S2(W, string(H, '.'));
        for (int i = 0; i < H; i++){
          for (int j = 0; j < W; j++){
            S2[j][i] = S[i][j];
          }
        }
        swap(S, S2);
        swap(H, W);
      }
      for (int i = 0; i < H; i++){
        cout << S[i] << endl;
      }
    }
  }
}