#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b)*b; }
template<class S,class T> ostream& operator << (ostream& out,const pair<S,T>& o){ out << "(" << o.first << "," << o.second << ")"; return out; }
template<class T> ostream& operator << (ostream& out,const vector<T>& V){ for(size_t i = 0; i < V.size(); i++){ out << V[i]; if(i!=V.size()-1) out << " ";} return out; }
template<class T> ostream& operator << (ostream& out,const vector<vector<T> >& Mat){ for(size_t i = 0; i < Mat.size(); i++) { if(i != 0) out << endl; out << Mat[i];} return out; }
template<class S,class T> ostream& operator << (ostream& out,const map<S,T>& mp){ out << "{ "; for(auto it = mp.begin(); it != mp.end(); it++){ out << it->first << ":" << it->second; if(mp.size()-1 != distance(mp.begin(),it)) out << ", "; } out << " }"; return out; }
template<typename T>vector<T> make_v(size_t a){return vector<T>(a);}
template<typename T,typename... Ts>auto make_v(size_t a,Ts... ts){return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));}
template<typename T,typename V> typename enable_if<is_class<T>::value==0>::type fill_v(T &t,const V &v){t=v;}
template<typename T,typename V> typename enable_if<is_class<T>::value!=0>::type fill_v(T &t,const V &v){for(auto &e:t) fill_v(e,v);}
/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

vector<vector<char>> simulate(int H,int W,int X){
    vector<vector<char>> ret(H,vector<char>(W,'.'));

    bool turn = false;
    vector<int> hind;
    for(int i = 1; i < H; i+=2){
        if(!turn){
            if(i+2 < H) hind.emplace_back(i);
            for(int j = 0; j < W-1; j++){ 
                ret[i][j] = '#'; 
            }
        }else{
            for(int j = 1; j < W; j++) ret[i][j] = '#';
        }
        turn = !turn;
    }

    int MaxX = -1;
    {
        vector<vector<int>> dist(H,vector<int>(W,INF));
        dist[0][0] = 0;
        queue<pii> q; q.emplace(0,0);

        int dir[4] = {1,0,-1,0};
        while(q.size()){
            int h,w;
            tie(h,w) = q.front(); q.pop();

            for(int k = 0; k < 4;k++){
                int nh = h + dir[k];
                int nw = w + dir[k^1];

                if(nh < 0 || nh >= H || nw < 0 || nw >= W){
                    continue;
                }
                if(ret[nh][nw] == '#') continue;

                if(dist[nh][nw] > dist[h][w] + 1){
                    dist[nh][nw] = dist[h][w] + 1;
                    q.emplace(nh,nw);
                }
            }
        }
        MaxX = dist[H-1][W-1];
    }
    if(X > MaxX || (MaxX - X)%4 != 0){
        return vector<vector<char>>{};
    }

    for(auto i : hind){
        if(MaxX == X) break;
        for(int j = W-3; j >= 0; j-= 2){
            if(MaxX == X) break;

            MaxX -= 4;
            swap(ret[i][j],ret[i][j+2]);
        }        
    }

    if(MaxX != X) return vector<vector<char>>{};
    return ret;
}
template<class Type>
Type solve(Type res = Type()){
    int H,W,X; cin >> H >> W >> X;

    {
        auto ret1 = simulate(H,W,X);
        if(!ret1.empty()){
            for(int i = 0; i < H;i++){
                for(int j = 0; j < W;j++){
                    cout << ret1[i][j];
                }cout << endl;
            }
            return res;
        }
    }
    {
        auto ret2 = simulate(W,H,X);
        if(!ret2.empty()){
            for(int i = 0; i < H; i++){
                for(int j = 0; j < W; j++){
                    cout << ret2[j][i];
                }cout << endl;
            }
            return res;
        }
    }

    cout << -1 << endl;
    return res;
}
int main(void) {
    cin.tie(0); ios::sync_with_stdio(false);
    solve<ll>(0);
    // cout << fixed << setprecision(12) << solve<ll>() << endl;
    return 0;
}