#include<iostream>
#include<vector>
using namespace std;
vector<string>calc(int H,int W,int X)
{
	vector<string>ret(H,string(W,'.'));
	if(H%4==1)
	{
		int mx=(H+1)/2*(W-1)+H-1;
		for(int i=1;i<H;i+=2)
		{
			if(i/2%2==0)
			{
				for(int j=0;j<W-1;j++)ret[i][j]='#';
			}
			else
			{
				for(int j=1;j<W;j++)ret[i][j]='#';
			}
		}
		vector<pair<int,int> >use;
		for(int i=1;i<H;i+=4)
		{
			for(int j=W-3;j>=0;j-=2)use.push_back(make_pair(i,j));
		}
		for(pair<int,int>p:use)
		{
			if(mx==X)break;
			ret[p.first][p.second]='.';
			ret[p.first-1][p.second+1]='#';
			mx-=4;
		}
		if(mx!=X)return vector<string>();
		else return ret;
	}
	else
	{
		int mx=(H-3)*(W+1)/2+(W-3)*2+4;
		for(int i=1;i<H-3;i+=2)
		{
			if(i/2%2==0)
			{
				for(int j=0;j<W-1;j++)ret[i][j]='#';
			}
			else
			{
				for(int j=1;j<W;j++)ret[i][j]='#';
			}
		}
		for(int j=1;j<W-3;j+=2)
		{
			if(j/2%2==0)
			{
				ret[H-3][j]=ret[H-2][j]='#';
			}
			else
			{
				ret[H-2][j]=ret[H-1][j]='#';
			}
		}
		ret[H-2][W-2]=ret[H-2][W-1]='#';
		vector<pair<int,int> >use;
		for(int i=1;i<H-3;i+=4)
		{
			for(int j=W-3;j>=0;j-=2)use.push_back(make_pair(i,j));
		}
		for(pair<int,int>p:use)
		{
			if(mx==X)break;
			ret[p.first][p.second]='.';
			ret[p.first-1][p.second+1]='#';
			mx-=4;
		}
		use.clear();
		for(int j=3;j<W-3;j+=4)
		{
			use.push_back(make_pair(H-1,j));
		}
		for(pair<int,int>p:use)
		{
			if(mx==X)break;
			ret[p.first][p.second]='.';
			ret[p.first-1][p.second-1]='#';
		}
		if(mx!=X)return vector<string>();
		else return ret;
	}
}
main()
{
	int H,W,X;
	cin>>H>>W>>X;
	if(H+W-2>X||(X-(H+W-2))%4!=0)
	{
		cout<<-1<<endl;
	}
	else if(H%4==1)
	{
		vector<string>ret=calc(H,W,X);
		if(ret.empty())cout<<-1<<endl;
		else
		{
			for(string s:ret)cout<<s<<endl;
		}
	}
	else
	{
		vector<string>ret=calc(W,H,X);
		if(ret.empty())cout<<-1<<endl;
		else
		{
			for(int i=0;i<H;i++)
			{
				for(int j=0;j<W;j++)cout<<ret[j][i];
				cout<<endl;
			}
		}
	}
}