#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);
  if(k%4 != 0){
    cout << -1 << "\n";
    return 0;
  }
  k /= 2;
  if(x < h + w - 2){
    cout << -1 << "\n";
    return 0;
  }
  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(x > max(H,W)){
    cout << -1 << "\n";
    return 0;
  }
  if(H >= W){
    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] = '#';
        }
      }
    }
  }
  rep(i,h)cout << res[i] << "\n";
  


  return 0;
}