#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;
//using mint = modint1000000007;
//using mint = modint998244353;

char f[1005][1005];

int main(){
  ll H, W, X;
  cin >> H >> W >> X;

  bool flip = false;
  if(H > W){
    flip = true;
    swap(H, W);
  }
  
  rep(i,H) rep(j,W) f[i][j] = '.';
  for(int i=1; i<W; i+=2){
    rep(j,H) f[j][i] = '#';
    if((i+1)%4!=0) f[H-1][i] = '.';
  }

  
  ll h = (H+1)/2;
  ll w = (W+1)/2;

  ll mn = (h-1)*2 + (w-1)*2;
  ll mx = 0;
  if((W-1)%4 == 0){
    mx = w*(h-1)*2 + (w-1)*2;

    if(X < mn || X > mx || (X-mn)%4!=0){
      cout << -1 << endl;
      return 0;
    }

    ll cnt = (mx-X)/4;
    vector<int> v;
    for(int i=3; i<W; i+=4) v.push_back(0);

    int p=0;
    while(cnt > 0){
      v[p]++;
      p++;
      if(p>=v.size()) p=0;
      cnt--;
    }
    for(int i=3; i<W; i+=4){
      f[2*v[(i-3)/4]][i] = '.';
    }
  }else{
    mx = (w-1)*(h-1)*2 + (w-1)*2;

    if(X < mn || X > mx || (X-mn)%4!=0){
      cout << -1 << endl;
      return 0;
    }

    ll cnt = (mx-X)/4;
    vector<int> v;
    for(int i=3; i<W; i+=4) v.push_back(0);

    int p=0;
    while(cnt > 0){
      v[p]++;
      p++;
      if(p>=v.size()) p=0;
      cnt--;
    }

    for(int i=3; i<W; i+=4){
      f[2*v[(i-3)/4]][i] = '.';
    }    
  }

  if(flip){
    rep(i,W){
      rep(j,H){
        cout << f[j][i];
      }
      cout << endl;
    }
  }else{
    rep(i,H){
      rep(j,W){
        cout << f[i][j];
      }
      cout << endl;
    }
  }
  
  return 0;
}