#include<bits/stdc++.h>
// #include<atcoder/all>
// #include<boost/multiprecision/cpp_int.hpp>

using namespace std;
// using namespace atcoder;
// using bint = boost::multiprecision::cpp_int;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define MOD 1000000007



int main(){
  
  int h,w,x;
  cin >> h >> w >> x;
  vector<string> res(h,string(w,'.'));
  rep(i,h)rep(j,w)if((i & 1) && (j & 1))res[i][j] = '#';
  int k = x - (h + w - 2);
  k /= 2;
  int H = (h-1)*(w/2) + (w/2)*2 + (w%4 == 1)*(h-1);
  int W = (w-1)*(h/2) + (h/2)*2 + (h%4 == 1)*(w-1);
  if(H >= W){
    assert(0);
    rep(i,w){
      if(i%2 == 0)continue;
      if(i%4 == 3){
        int up = min(k,h-1);
        k -= up;
        for(int j = h-1;j >= 0;j -= 2){
          if(j != h-1-up)res[j][i] = '#';
        }
      }else{
        for(int j = h-3;j >= 0;j -= 2){
          res[j][i] = '#';
        }
      }
    }
  }else{
    rep(i,h){
      if(i%2 == 0)continue;
      if(i%4 == 3){
        int up = min(k,w-1);
        k -= up;
        for(int j = w-1;j >= 0;j -= 2){
          if(j != w-1-up)res[i][j] = '#';
        }
      }else{
        for(int j = w-3;j >= 0;j -= 2){
          res[i][j] = '#';
        }
      }
    }
  }
  vector<vector<int>> d(h,vector<int>(w,-1));
  d[0][0] = 0;
  queue<P> que;
  que.push({0,0});
  int dx[] = {0,1,0,-1};
  int dy[] = {-1,0,1,0};
  while(!que.empty()){
    P ov = que.front();que.pop();
    rep(i,4){
      P nv = {ov.first + dy[i],ov.second + dx[i]};
      if(nv.first < 0 || nv.first >= h || nv.second < 0 || nv.second >= w)continue;
      if(res[nv.first][nv.second] == '#')continue;
      if(d[nv.first][nv.second] != -1)continue;
      d[nv.first][nv.second] = d[ov.first][ov.second] + 1;
      que.push(nv);
    }
  }
  if(d[h-1][w-1] == x)rep(i,h)cout << res[i] << "\n";
  else cout << -1 << "\n";
  


  return 0;
}