using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
using System.Threading;
using System.Runtime.CompilerServices;
using System.Diagnostics;
//using nint=System.Int32;
static class Program{
	const int mod=(int)1e9+7;
	static void Main(){
		Sc sc=new Sc();
		var s=sc.Ia;
		var p=s[0]+s[1]-2;
		if(s[2]<p||(s[2]-p)%4!=0){
			Console.WriteLine("{0}",-1);
			return;
		}
		var c=new char[s[0]][];
		for(int i = 0;i<s[0];i++) {
			c[i]=new char[s[1]];
			for(int j = 0;j<s[1];j++) {c[i][j]=(i&j&1)==0?'.':'#';}
		}
		var g=-1;
		var bb=false;
		for(int i = 1;i<s[0]-(s[0]/2%2==0?0:2);i+=2) {
			if(((i>>1)&1)==1){
				for(int j = s[1]-1;j>0;j-=2) {
					if(j==g){continue;}
					c[i][j]='#';
					if(g==-1){p+=4;}
					if(p==s[2]&&g==-1){g=j-2;}
				}
			}
			else{
				for(int j = 0;j<s[1]-2;j+=2) {
					if(j==g){continue;}
					c[i][j]='#';
					if(i==1){continue;}
					if(g==-1){p+=4;}
					if(p==s[2]&&g==-1){
						g=0;
						j+=2;
						if(j==s[1]-1){bb=true;}
					}
				}
			}
			if(g!=-1){
				if(g!=0){c[i][0]='#';}
				if(g!=s[1]-1&&!bb){c[i][s[1]-1]='#';}
				bb=false;
			}
		}
		if(s[0]/2%2==1){
			var bo=false;
			if(p>=s[2]){bo=true;}
			c[s[0]-3][1]='#';
			for(int j = 3;j<s[1];j+=2) {
				if(p<s[2]){
					c[s[0]-1-(((j>>1)&1)^1)*2][j]='#';
					p+=4;
				}
				else{
					bo=true;
					c[s[0]-3][j]='#';
				}
			}
			if(s[0]/2%2==1&&s[1]/2%2==1&&!bo&&p==s[2]){
				Console.WriteLine(-1);
				return;
			}
		}
		if(p<s[2]){
			Console.WriteLine(-1);
			return;
		}
		StringBuilder sb=new StringBuilder();
		for(int i = 0;i<s[0];i++) {sb.Append(string.Join("",c[i])+"\n");}
		Console.Write(sb);
	}
}

public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),int.Parse);}
	public int[] Ia3(int a){return Array.ConvertAll((Console.ReadLine()+" "+a.ToString()).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),long.Parse);}
	public long[] La3(int a){return Array.ConvertAll((Console.ReadLine()+" "+a.ToString()).Split(),long.Parse);}
	public double[] Da2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),double.Parse);}}
	public double[] Da3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),double.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
	public (T,T) Tp2<T>(){var s=Console.ReadLine().Split();return (Ct<T>(s[0]),Ct<T>(s[1]));}
	public (T,T,T) Tp3<T>(){var s=Console.ReadLine().Split();return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]));}
	public (T1,T1,T2) Tp3<T1,T2>(){var s=Console.ReadLine().Split();return (Ct<T1>(s[0]),Ct<T1>(s[1]),Ct<T2>(s[2]));}
	private T Ct<T>(string s){return (T)Convert.ChangeType(s,typeof(T));}
}