#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define each(e, v) for(auto &e: v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
//const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

struct io_setup{
    io_setup(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

int main(){
    int H, W, K; cin >> H >> W >> K;

    if(K&1) {cout << "-1\n"; return 0;}
    K >>= 1;

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

    if(K%2 != (h+w)%2) {cout << "-1\n"; return 0;}

    if(h%2 == 0 && w%2 == 0){
        if(K < h+w-2 || h*w-2 < K) {cout << "-1\n"; return 0;}

        K = (h*w-2)-K, K /= 2;

        int a = (h-2)/2;

        vector<int> r(a, w-1);

        rep(i, a){
            int tmp = min(K, r[i]);
            r[i] -= tmp, K -= tmp;
        }

        int b = (w-2)/2-K;

        vector<string> S(H, string(W, '#'));

        rep(i, a){
            fill(all(S[4*i]), '.'), fill(all(S[4*i+2]), '.');
            S[4*i+1][2*r[i]] = '.',  S[4*i+3][0] = '.'; 
        }

        S[H-3][0] = S[H-2][0] = '.';
        rep(j, W) S[H-1][j] = '.';

        rep(i, (w-2)/2){
            if(i < b){
                S[H-3][4*i+2] = S[H-3][4*i+3] = S[H-3][4*i+4] = '.';
                S[H-2][4*i+2] = S[H-2][4*i+4] = '.';
                S[H-1][4*i+3] = '#';
            }
        }

        rep2(j, 4*b, W-1) S[H-3][j] = '.';

        rep(i, H) cout << S[i] << '\n';
    }
    else{
        bool rev = false;
        if(h%2 == 0) rev = true, swap(h, w), swap(H, W);

        if(K < h+w-2 || h*w-1 < K) {cout << "-1\n"; return 0;}

        K = (h*w-1)-K, K /= 2;

        int a = (h-1)/2;

        vector<int> r(a, w-1);

        rep(i, a){
            int tmp = min(K, r[i]);
            r[i] -= tmp, K -= tmp;
        }

        vector<string> S(H, string(W, '#'));

        rep(i, a){
            fill(all(S[4*i]), '.'), fill(all(S[4*i+2]), '.');
            S[4*i+1][2*r[i]] = '.',  S[4*i+3][0] = '.'; 
        }

        fill(all(S[H-1]), '.');

        if(!rev){
            rep(i, H) cout << S[i] << '\n';
        }
        else{
            rep(j, W){
                rep(i, H) cout << S[i][j];
                cout << '\n';
            }
        }
    }
}