import java.util.*;
import java.io.*;

public class Main {
    static FastScanner sc = new FastScanner(System.in);
    static PrintWriter pw = new PrintWriter(System.out);
    static StringBuilder sb = new StringBuilder();

    public static void main(String[] args) throws Exception {
        if (args.length == 1 && args[0].equals("debug")) {
            FileReader filereader;
            BufferedReader is;
            String path = new File(".").getAbsoluteFile().getParent();
            String input = path + File.separator + "_debug_";
            String output = path + File.separator + "_answer_" + File.separator;
            File[] list = new File(input).listFiles();
            for (File file : list) {
                filereader = new FileReader(file);
                sc = new FastScanner(filereader);
                pw.println(file.getName());
                pw.println("----------------------------------------");
                pw.println("output");
                long start = System.currentTimeMillis();
                solve();
                if (new File(output + file.getName()).exists()) {
                    pw.println("----------------------------------------");
                    pw.println("expect");
                    filereader = new FileReader(new File(output + file.getName()));
                    is = new BufferedReader(filereader);
                    String s;
                    while ((s = is.readLine()) != null) {
                        pw.println(s);
                    }
                }
                pw.println("----------------------------------------");
                pw.println((System.currentTimeMillis() - start) + "ms\n");
            }
        } else {
            solve();
        }
        pw.flush();
    }

    public static void solve() {
        int h = sc.nextInt();
        int w = sc.nextInt();
        int x = sc.nextInt();
        char[][] map = new char[h][w];
        int hmax = ((h-1)/2) % 2 == 0 ? (h+1)/2 : (h-1)/2;  
        int wmax = ((w-1)/2) % 2 == 0 ? (w+1)/2 : (w-1)/2;  
        int max = Math.max(hmax*(w-1)+(h-1),wmax*(h-1)+(w-1));
        if((h-1+w-1) > x || max < x || x % 2 != 0){
            pw.println(-1);
            return;
        }else{
            int rem = x - (h-1+w-1);
            if(rem % 4 != 0){
                pw.println(-1);
                return;
            }
            if(hmax*(w-1)+(h-1) >= wmax*(h-1)+(w-1)){
                int j = 0;
                for(int i = 0; i < h; i++){
                    if(i == h-1){
                        for(int k = 0; k < w; k++){
                            map[i][k] = '.';
                        }
                    }else if(i % 2 != 0){
                        for(int k = 0; k < w; k++){
                            if(k != j){
                                map[i][k] = '#';
                            }else{
                                map[i][k] = '.';
                            }
                        }
                    }else{
                        int next = Math.min(rem/2,Math.max(w-1-j,j));
                        if(j+next < w && (i/2) % 2 == 0){
                            for(int k = 0; k < w; k++){
                                map[i][k] = '.';
                            }
                            j += next;
                        }else{
                            for(int k = 0; k < w; k++){
                                map[i][k] = '.';
                            }
                            j -= next;
                            rem -= next*2;
                        }
                    }
                }
            }else{
                int i = 0;
                for(int j = 0; j < w; j++){
                    if(j == w-1){
                        for(int k = 0; k < h; k++){
                            map[k][j] = '.';
                        }
                    }else if(j % 2 != 0){
                        for(int k = 0; k < h; k++){
                            if(k != i){
                                map[k][j] = '#';
                            }else{
                                map[k][j] = '.';
                            }
                        }
                    }else{
                        int next = Math.min(rem/2,Math.max(h-1-i,i));
                        for(int k = 0; k < h; k++){
                            map[k][j] = '.';
                        }
                        if(i+next < h && (j/2) % 2 == 0){
                            i += next;
                        }else{
                            i -= next;
                            rem -= next*2;
                        }
                    }
                }
            }
        }
        for(int i = 0; i < h; i++) pw.println(new String(map[i]));
    }

    static class GeekInteger {
        public static void save_sort(int[] array) {
            shuffle(array);
            Arrays.sort(array);
        }

        public static int[] shuffle(int[] array) {
            int n = array.length;
            Random random = new Random();
            for (int i = 0, j; i < n; i++) {
                j = i + random.nextInt(n - i);
                int randomElement = array[j];
                array[j] = array[i];
                array[i] = randomElement;
            }
            return array;
        }

        public static void save_sort(long[] array) {
            shuffle(array);
            Arrays.sort(array);
        }

        public static long[] shuffle(long[] array) {
            int n = array.length;
            Random random = new Random();
            for (int i = 0, j; i < n; i++) {
                j = i + random.nextInt(n - i);
                long randomElement = array[j];
                array[j] = array[i];
                array[i] = randomElement;
            }
            return array;
        }
    }
}

class FastScanner {
    private BufferedReader reader = null;
    private StringTokenizer tokenizer = null;

    public FastScanner(InputStream in) {
        reader = new BufferedReader(new InputStreamReader(in));
        tokenizer = null;
    }

    public FastScanner(FileReader in) {
        reader = new BufferedReader(in);
        tokenizer = null;
    }

    public String next() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

    public String nextLine() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                return reader.readLine();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken("\n");
    }

    public long nextLong() {
        return Long.parseLong(next());
    }

    public int nextInt() {
        return Integer.parseInt(next());
    }

    public double nextDouble() {
        return Double.parseDouble(next());
    }

    public String[] nextArray(int n) {
        String[] a = new String[n];
        for (int i = 0; i < n; i++)
            a[i] = next();
        return a;
    }

    public int[] nextIntArray(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = nextInt();
        return a;
    }

    public long[] nextLongArray(int n) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++)
            a[i] = nextLong();
        return a;
    }
}