#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;

using ll=long long;
using ldub=long double;
using lldub=__float128;
using str=string;

using mint=modint;

template<class T=ll>
using tup2=tuple<T,T>;
template<class T=ll>
using tup3=tuple<T,T,T>;
template<class T=ll>
using tup4=tuple<T,T,T,T>;
template<class T=ll>
using tup5=tuple<T,T,T,T,T>;
template<class T=ll>
using tup6=tuple<T,T,T,T,T,T>;
template<class T=ll>
using tup7=tuple<T,T,T,T,T,T,T>;

template<class T=ll>
using vec=vector<T>;
template<class T=ll>
using vec2=vector<vec<T>>;
template<class T=ll>
using vec3=vector<vec2<T>>;
template<class T=ll>
using vec4=vector<vec3<T>>;
template<class T=ll>
using vec5=vector<vec4<T>>;
template<class T=ll>
using vec6=vector<vec5<T>>;

template<class T>
using que=queue<T>;
template<class T>
using Pque=priority_queue<T>;
template<class T>
using pque=priority_queue<T, vector<T>, greater<T>>;

struct Edge{
  ll from,to,w=1,num=-1;
};
using gvec=vector<Edge>;
using gvec2=vector<gvec>;

template<class T>
bool chmax(T &a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>
bool chmin(T &a,T b){if(b<a){a=b;return 1;}return 0;}

#define pb push_back
#define pf push_front
#define pob pop_back
#define pof pop_front
#define ins insert
#define tup make_tuple
#define low lower_bound
#define pops(a) __builtin_popcountll(a)
#define ctz(a) __builtin_ctzll(a)
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define nperm(v) next_permutation(all(v))
#define Yes cout << "Yes" << endl
#define No cout << "No" << endl
#define YN(f) cout << ((f)?"Yes":"No") << endl

const int IINF=2e9;
const ll INF=4e18;

#ifndef LOCAL
#define debug(x)
#endif




// =================================================




void solve(){
  ll H,W,K;
  cin >> H >> W >> K;
  vec2<char> A(H,vec<char>(W,'.'));
  if(K==0){

  }else if(H==1|W==1){
    if(K!=1){
      cout << -1 << endl;
      return;
    }
    A[0][0]='#';
  }else if(K==1||K>H*W-H-W+2){
    cout << -1 << endl;
    return;
  }else if(K<H){
    for(ll i=0;i<K-1;i++) A[i][0]='#';
  }else{
    for(ll i=0;i<H;i++){
      A[i][0]='#';
      for(ll j=1;j<W-1;j++) if((i&1)==0) A[i][j]='#';
    }
    debug(A);
    ll X=(H*W-H-W+2)-K;
    for(ll i=(H-1)/2*2;i>=0;i-=2){
      for(ll j=W-2;j>0;j--){
        if(X==0||(X==1&&i!=0&&i!=H-1)) continue;
        if(i==0||i==H-1) X--;
        else X-=2;
        A[i][j]='.';
      }
    }
    if(X==1){
      X--;
      A[0][W-2]='.';
    }
  }
  for(ll i=0;i<H;i++){
    for(ll j=0;j<W;j++) cout << A[i][j];
    cout << endl;
  }
}

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  mint::set_mod(998244353);
  // mint::set_mod(1000000007);

  ll T=1;
  // cin >> T;
  while(T--) solve();
  return 0;
}