#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using namespace std;

typedef long long ll;

vector<string> solve(int H, int W, int X) {
    int minX = H + W - 2;
    if (X < minX) return {"-1"};
    int A = X - minX;
    if (A % 4) return {"-1"};
    vector<string> ret(H);
    rep(i, H) {
        if (i % 2) {
            rep(j, W - 1) ret[i].push_back('#');
            ret[i].push_back('.');
        } else {
            rep(j, W) ret[i].push_back('.');
        }
    }
    if (H % 4 == 1) {
        int maxX = (W - 1) * (H + 1) / 2 + H - 1;
        if (X > maxX) return {"-1"};
        int dx = X - minX, p = (W - 1) * 2, q = dx / p, r = dx % p;
        //cout << "dx=" << dx << " p=" << p << " q=" << q << " r=" << r << "\n"; 
        rep(i, q) {
            ret[i * 4 + 3][0] = '.';
            ret[i * 4 + 3][W - 1] = '#';
        }
        ret[q * 4 + 3][W - 1] = '#';
        ret[q * 4 + 3][W - 1 - r / 2] = '.';
        return ret;
    }
    if (W % 4 == 1) {
        vector<string> r = solve(W, H, X);
        rep(i, H) rep(j, W) ret[i][j] = r[j][i];
        return ret;
    }
    int maxX = (W - 1) * (H - 1) / 2 + H - 1 + W / 4 * 4;
    //cout << "maxX=" << maxX << "\n";
    if (X > maxX) return {"-1"};
    int dx = X - minX, p = (W - 1) * 2, q = dx / p, r = dx % p;
    //cout << "dx=" << dx << " p=" << p << " q=" << q << " r=" << r << "\n"; 
    if (q > H / 4) {
        r += (q - H / 4) * p;
        q = H / 4;
    }
    rep(i, q) {
        ret[i * 4 + 3][0] = '.';
        ret[i * 4 + 3][W - 1] = '#';
    }
    if (r > 0 && q * 4 + 3 < H && W - 1 - r / 2 >= 0) {
        ret[q * 4 + 3][W - 1] = '#';
        ret[q * 4 + 3][W - 1 - r / 2] = '.';
        return ret;
    }
    rep(i, r / 4) {
        ret[H - 2][i * 4] = '.';
        ret[H - 3][i * 4 + 1] = '#';
        ret[H - 2][i * 4 + 2] = '.';
        ret[H - 1][i * 4 + 3] = '#';
    }
    return ret;
}

int main() {
    int H, W, X;
    cin >> H >> W >> X;
    vector<string> ans = solve(H, W, X);
    rep(i, ans.size()) cout << ans[i] << "\n";
}