//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using ll = int64_t;
using ull = uint64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T>>;
const int INF = 0xccccccc;
const ll LINF = 0xcccccccccccccccLL;
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);}
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);}
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second;}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << ' ' << p.second;}



//head



int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int h, w, x;
  cin >> h >> w >> x;
  int l = h+w-2, r = h*w-(h/2)*(w/2)*2-1;
  bool reigai = (h&2 and w&2);
  if(h&2 and w&2) r -= 2;
  if(x < l or r < x or (x-l)&3) {
    puts("-1");
    return 0;
  }
  vs ans(h, string(w, '.'));
  int u = l;
  if(reigai) {
    rep(i, h/2-1) rep(j, w/2) {
      if(u != x or i&1) {
        ans[i*2+1][j*2+1] = ans[i*2+1][j*2+2*(i&1)] = '#';
        if(~i&1) u += 4;
      }
      else ans[i*2+1][j*2+1] = ans[i*2+1][j*2+2] = '#';
    }
    rep(j, w/2) {
      if(u != x) {
        ans[h-2][j*2+1] = ans[h-1-2*(~j&1)][j*2+1] = '#';
        if(j&1) u += 4;
      }
      else ans[h-2][j*2+1] = ans[h-3][j*2+1] = '#';
    }
  }
  else {
    bool rev = h&1;
    if(rev) swap(h, w);
    vs a__(h, string(w, '.'));
    rep(i, h/2) rep(j, w/2) {
      if(u != x or i&1) {
        a__[i*2+1][j*2+1] = a__[i*2+1][j*2+2*(i&1)] = '#';
        if(~i&1) u += 4;
      }
      else a__[i*2+1][j*2+1] = a__[i*2+1][j*2+2] = '#';
    }
    if(rev) swap(h, w);
    rep(i, h) rep(j, w) {
      if(rev) ans[i][j] = a__[j][i];
      else ans[i][j] = a__[i][j];
    }
  }
  rep(i, h) cout << ans[i] << '\n';
}