#include <bits/stdc++.h>
//#include<boost/multiprecision/cpp_int.hpp>
//#include<boost/multiprecision/cpp_dec_float.hpp>
//#include <atcoder/all>
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i)
#define repl(i, a) for (ll i = (ll)0; i < (ll)a; ++i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define popcount __builtin_popcount
#define fi first
#define se second
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll mod_998244353 = 998244353;
constexpr ll INF = 1LL << 60;

// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

//using lll=boost::multiprecision::cpp_int;
//using Double=boost::multiprecision::number<boost::multiprecision::cpp_dec_float<1024>>;//仮数部が1024桁
template <class T>
inline bool chmin(T &a, T b)
{
	if (a > b)
	{
		a = b;
		return true;
	}
	return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
	if (a < b)
	{
		a = b;
		return true;
	}
	return false;
}

template <typename T>
T mypow(T x, T n, const T &p = -1)
{ //x^nをmodで割った余り

	if (p != -1)
	{
		x %= p;
	}
	T ret = 1;
	while (n > 0)
	{
		if (n & 1)
		{
			if (p != -1)
				ret = (ret * x) % p;
			else
				ret *= x;
		}
		if (p != -1)
			x = (x * x) % p;
		else
			x *= x;
		n >>= 1;
	}
	return ret;
}

using namespace std;
//using namespace atcoder;

void solve()
{
	int h,w,x;
	cin>>h>>w>>x;
	int minv=h-1+w-1;
	int maxv=(h+int(h/2%2==0))/2*w-int(h/2%2==0)+h/2;
	int maxv2=(w+int(w/2%2==0))/2*h-int(w/2%2==0)+w/2;

	string s;
	rep(i,w)s+=".";
	vector<string>ans(h,s);
	if(maxv>=maxv2){
		for(int i=1;i<h;i+=2){
			if((i/2)%2==0){
				rep(j,w-1){
				ans[i][j]='#';
				}
			}else{
				for(int j=w-1;j>0;--j){
					ans[i][j]='#';
				}
			}
		}
		if(x<minv||x>maxv){
			cout<<-1<<"\n";
			return;
		}
		if((maxv-x)%4){
			cout<<-1<<"\n";
			return;
		}

		for(int i=w-3;i>=0;i-=2){
			if(maxv-x==(w-1-i)*2){
				ans[1][i]='.';
				ans[0][i+1]='#';
				break;
			}
		}
	}else{
		
		for(int i=1;i<w;i+=2){
			if((i/2)%2==0){
				rep(j,h-1){
					ans[j][i]='#';
				}
			}else{
				for(int j=h-1;j>0;--j){
					ans[j][i]='#';
				}
			}
		}
		chmax(maxv,maxv2);
		if(x<minv||x>maxv){
			cout<<-1<<"\n";
			return;
		}
		if((maxv-x)%4){
			cout<<-1<<"\n";
			return;
		}

		for(int i=h-3;i>=0;i-=2){
			if(maxv-x==(h-1-i)*2){
				ans[i][1]='.';
				ans[i+1][0]='#';
				break;
			}
		}
	}
	
	rep(i,h){
		cout<<ans[i]<<"\n";
	}
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}