#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> res1(h,string(w,'.'));
  rep(i,h)rep(j,w)if((i & 1) && (j & 1))res1[i][j] = '#';
  int k = x - (h + w - 2);
  k /= 2;
  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)res1[j][i] = '#';
      }
    }else{
      for(int j = h-3;j >= 0;j -= 2){
        res1[j][i] = '#';
      }
    }
  }
  auto ok = [&](vector<string> &res){
    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);
      }
    }
    return d[h-1][w-1] == x;
  };
  if(ok(res1)){
    rep(i,h)cout << res1[i] << "\n";
    return 0;
  }
  vector<string> res2(h,string(w,'.'));
  rep(i,h)rep(j,w)if((i & 1) && (j & 1))res2[i][j] = '#';
  k = x - (h + w - 2);
  k /= 2;
  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)res2[i][j] = '#';
      }
    }else{
      for(int j = w-3;j >= 0;j -= 2){
        res2[i][j] = '#';
      }
    }
  }
  if(ok(res2)){
    rep(i,h)cout << res2[i] << "\n";
    return 0;
  }
  cout << "-1\n";
  


  return 0;
}