#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
//constexpr ll MOD = 1e9 + 7;
constexpr ll MOD = 998244353;
//constexpr ll MOD = ;
ll mod(ll A, ll M) {return (A % M + M) % M;}
constexpr ll INF = 1LL << 60;
template<class T> bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
ll divceil(ll A, ll B) {return (A + (B - 1)) / B;}
#define FINALANS(A) do {cout << (A) << '\n'; exit(0);} while (false)

int main()
{
  ll H, W, X;
  cin >> H >> W >> X;
  
  if (X % 2 == 1)
    FINALANS(-1);
  ll h = (H + 1) / 2, w = (W + 1) / 2, x = X / 2;

  vector<string> S(H, string(W, '#'));
  

  if (h % 2 == 0 && w % 2 == 0)
  {
    if (!(h + w - 2 <= x && x <= h * w - 1))
      FINALANS(-1);
    if ((x - (h + w - 2)) % 2 != 0)
      FINALANS(-1);

    for (ll i = 0; i < H; i++)
    {
      S.at(i).at(0) = '.';
    }
    for (ll j = 0; j < W; j++)
    {
      for (ll i = 0; i < H; i += 2)
      {
        S.at(i).at(j) = '.';
      }
    }

    ll cnt = 0;
    for (ll i = 0; i + 2 < H - 1; i += 4)
    {
      for (ll j = 0; j + 2 < W; j += 2)
      {
        if (cnt == (x - (h + w - 2)) / 2)
          goto FIN;

        S.at(i).at(j + 1) = '.', S.at(i).at(j + 2) = '.';
        S.at(i + 1).at(j) = '#', S.at(i + 1).at(j + 2) = '.';
        S.at(i + 2).at(j + 1) = '.', S.at(i + 2).at(j + 2) = '.';

        cnt++;
      }
    }
    for (ll j = 2; j + 2 < W; j += 4)
    {
      if (cnt == (x - (h + w - 2)) / 2)
        goto FIN;

      S.at(H - 3).at(j) = '.', S.at(H - 2).at(j) = '.';
      S.at(H - 3).at(j + 1) = '.', S.at(H - 1).at(j + 1) = '#';
      S.at(H - 3).at(j + 2) = '.', S.at(H - 2).at(j + 2) = '.';

      cnt++;
    }

    if (cnt == (x - (h + w - 2)) / 2)
      goto FIN;
  }
  else
  {
    if (!(h + w - 2 <= x && x <= h * w))
      FINALANS(-1);
    if ((x - (h + w - 2)) % 2 != 0)
      FINALANS(-1);

    if (h % 2 != 0)
    {
      for (ll i = 0; i < H; i++)
      {
        S.at(i).at(0) = '.';
      }
      for (ll j = 0; j < W; j++)
      {
        for (ll i = 0; i < H; i += 2)
        {
          S.at(i).at(j) = '.';
        }
      }

      ll cnt = 0;
      for (ll i = 0; i + 2 < H; i += 4)
      {
        for (ll j = 0; j + 2 < W; j += 2)
        {
          if (cnt == (x - (h + w - 2)) / 2)
            goto FIN;
          
          S.at(i).at(j + 1) = '.', S.at(i).at(j + 2) = '.';
          S.at(i + 1).at(j) = '#', S.at(i + 1).at(j + 2) = '.';
          S.at(i + 2).at(j + 1) = '.', S.at(i + 2).at(j + 2) = '.';

          cnt++;
        }
      }

      if (cnt == (x - (h + w - 2)) / 2)
        goto FIN;
    }
    else
    {
      for (ll i = 0; i < H; i++)
      {
        for (ll j = 0; j < W; j += 2)
        {
          S.at(i).at(j) = '.';
        }
      }
      for (ll j = 0; j < W; j++)
      {
        S.at(0).at(j) = '.';
      }

      ll cnt = 0;
      for (ll j = 0; j + 2 < W; j += 4)
      {
        for (ll i = 0; i + 2 < H; i += 2)
        {
          if (cnt == (x - (h + w - 2)) / 2)
            goto FIN;
          
          S.at(i + 1).at(j) = '.', S.at(i + 2).at(j) = '.';
          S.at(i).at(j + 1) = '#', S.at(i + 2).at(j + 1) = '.';
          S.at(i + 1).at(j + 2) = '.', S.at(i + 2).at(j + 2) = '.';

          cnt++;
        }
      }

      if (cnt == (x - (h + w - 2)) / 2)
        goto FIN;
    }

    FIN:
    for (ll i = 0; i < H; i++)
    {
      cout << S.at(i) << endl;
    }

    //cerr << (h + w - 1) << " " << x << endl;
  }
}