#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

vector<string> get(int H,int W,int X,vector<string> S){
	if(H<=3){
		return {};
	}
	int XX = X;
	auto T = S;

	rep(i,H){
		if(i&1){
			rep(j,W){
				T[i][j] = '#';
			}
		}
	}
	
	for(int i=1;i<H;){
		if(i+4>=H||i+6<H){
			T[i].back() = '.';
			i += 2;
			int cur = W-1;
			while(cur!=0&&X>0){
				X -= 4;
				cur -= 2;
			}
			T[i][cur] = '.';
			i+=2;
		}
		else{
			T[i].back() = '.';
			i += 2;
			int cur = W-1;
			while(cur!=0&&X>0){
				X -= 4;
				cur -= 2;
			}
			T[i][cur] = '.';
			i += 2;
			T[i][cur] = '.';
			if(cur==0&&X>0){
				
			//	T[i-1][1] = '#';
				
				int x = 2;
				while(x+2<W && X>0){
					X -= 4;
					T[i-1][x-1] = '#';
					T[i][x] = '.';
					T.back()[x+1] = '#';
					T[i][x+2] = '.';
					x += 4;
				}
				
				
			}
			i += 2;
		}
	}
	
	
	if(X==0){
		return T;
	}
	return {};
	
}

int main(){
	
	int H,W,X;
	cin>>H>>W>>X;
	
	vector<string> S(H,string(W,'.'));
	rep(i,H){
		rep(j,W){
			if(i&1){
				if(j&1){
					S[i][j] = '#';
				}
			}
		}
	}
	
	X -= (H-1) + (W-1);
	if(X<0){
		cout<<-1<<endl;
		return 0;
	}
	
	if(X%4!=0){
		cout<<-1<<endl;
		return 0;
	}
	
	if(X==0){
		rep(i,H){
			if(i&1){
				rep(j,W-1)S[i][j] = '#';
			}
		}
		rep(i,H){
			cout<<S[i]<<endl;
		}
		return 0;
	}
	
	auto ret = get(H,W,X,S);
	if(ret.size()!=0){
		
		rep(i,H)cout<<ret[i]<<endl;
		return 0;
	}
	
	vector<string> SS(W,string(H,'.'));
	rep(i,H){
		rep(j,W){
			SS[j][i] = S[i][j];
		}
	}
	ret = get(W,H,X,SS);
	if(ret.size()==0)cout<<-1<<endl;
	else{
		rep(i,H){
			rep(j,W){
				S[i][j] = ret[j][i];
			}
		}
		rep(i,H)cout<<S[i]<<endl;
	}
	
	
    return 0;
}