#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

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;
	}
	
	{	
		int XX = X;
		auto T = S;

		for(int i=1;i<H;i+=2){
			if(i==1){
				rep(j,W-1)T[i][j] = '#';
			}
			else{
				if(i+2>H){
					rep(j,W-1)T[i][j] = '#';
					break;
				}
				int cur = W-1;
				while(cur!=0&&X>0){
					X -= 4;
					cur -= 2;
				}
				rep(j,W){
					if(j==cur)continue;
					T[i][j] = '#';
				}
				
				i+=2;
				if(i<H){
					rep(j,W-1){
						T[i][j] = '#';
					}
				}
				
				
			}
		}
		if(X==0){
			rep(i,H)cout<<T[i]<<endl;
			return 0;
		}
		X = XX;
	}
	
	{	
		int XX = X;
		auto T = S;

		for(int i=1;i<W;i+=2){
			if(i==1){
				rep(j,H-1)T[j][i] = '#';
			}
			else{
				if(i+2>W){
					rep(j,H-1)T[j][i] = '#';
					break;
				}
				int cur = H-1;
				while(cur!=0&&X>0){
					X -= 4;
					cur -= 2;
				}
				rep(j,H){
					if(j==cur)continue;
					T[j][i] = '#';
				}
				
				i+=2;
				if(i<W){
					rep(j,H-1){
						T[j][i] = '#';
					}
				}
				
				
			}
		}
		if(X==0){
			rep(i,H)cout<<T[i]<<endl;
			return 0;
		}
		X = XX;
	}
	
	cout<<-1<<endl;
	
	
    return 0;
}