#pragma GCC optimize("Ofast")
//#pragma GCC target ("sse4")

#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<cassert>
#include<complex>
#include<numeric>
#include<array>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
constexpr ll mod = 998244353;
const ll INF = mod * mod;
typedef pair<int, int>P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-12;
const ld pi = acosl(-1.0);

ll mod_pow(ll x, ll n, ll m = mod) {
	if (n < 0) {
		ll res = mod_pow(x, -n, m);
		return mod_pow(res, m - 2, m);
	}
	if (abs(x) >= m)x %= m;
	if (x < 0)x += m;
	ll res = 1;
	while (n) {
		if (n & 1)res = res * x % m;
		x = x * x % m; n >>= 1;
	}
	return res;
}
struct modint {
	ll n;
	modint() :n(0) { ; }
	modint(ll m) :n(m) {
		if (n >= mod)n %= mod;
		else if (n < 0)n = (n % mod + mod) % mod;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint& a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; }
modint operator-=(modint& a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; }
modint operator*=(modint& a, modint b) { a.n = ((ll)a.n * b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, ll n) {
	if (n == 0)return modint(1);
	modint res = (a * a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }
modint operator/=(modint& a, modint b) { a = a / b; return a; }
const int max_n = 1 << 24;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}
modint combP(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[a - b];
}


int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
void solve() {
	int h, w; cin >> h >> w;
	int x; cin >> x;
	if (x % 2) {
		cout << -1 << "\n"; return;
	}
	x /= 2;
	int dh = (h + 1) / 2;
	int dw = (w + 1) / 2;
	bool bs = false;
	if (dw % 2) {
		swap(h, w);
		swap(dh, dw);
		bs = true;
	}
	vector<string> ans(h);
	rep(i, h) {
		ans[i].resize(w,'#');
	}
	vector<P> vs;
	if (dh % 2 == 0) {
		int le = dh + dw - 2;
		int ri = dh * dw - 2;
		if (le <= x && x <= ri&&(x-le)%2==0) {
			int rest = (x - le) / 2;
			vs.push_back({ dh - 1,dw - 1 });
			for (int i = dh - 3; i >= 0; i -= 2) {
				vs.push_back({ i+1,dw - 1 });
				if (rest > 0) {
					rest--;
					vs.push_back({ i + 1,dw - 2 });
					vs.push_back({ i,dw - 2 });
				}
				vs.push_back({ i,dw - 1 });
			}
			vs.push_back({ 0,dw - 1 });
			vs.push_back({ 0,dw - 2 });
			for (int j = dw - 4; j >= 0; j -= 2) {
				vs.push_back({ 0,j + 1 });
				int num = min(rest, dh - 1);
				rest -= num;
				for (int i = 1; i <= num; i++) {
					vs.push_back({ i,j + 1 });
				}
				for (int i = num; i >= 1; i--) {
					vs.push_back({ i,j });
				}
				vs.push_back({ 0,j });
			}
		}
		else {
			cout << -1 << "\n"; return;
		}
	}
	else {
		int le = dh + dw - 2;
		int ri = dh * dw - 1;
		if (le <= x && x <= ri && (x - le) % 2 == 0) {
			int rest = (x - le) / 2;
			for (int i = dh - 2; i >= 0; i -= 2) {
				vs.push_back({ i + 1,dw - 1 });
				int num = min(rest, dw - 1);
				rest -= num;
				for (int j = 0; j < num; j++) {
					vs.push_back({ i + 1,dw - 2 - j });
				}
				for (int j = num - 1; j >= 0; j--) {
					vs.push_back({ i,dw - 2 - j });
				}
				vs.push_back({ i,dw - 1 });
			}
			for (int j = dw - 1; j >= 0; j--)vs.push_back({ 0,j });
		}
		else {
			cout << -1 << "\n"; return;
		}
	}
	rep(i, h)rep(j, w) {
		if (i % 2 == 0&&j%2==0)ans[i][j] = '.';
	}
	rep(i, vs.size() - 1) {
		int cx = vs[i].first;
		int cy = vs[i].second;
		int nx = vs[i + 1].first;
		int ny = vs[i + 1].second;
		rep(d, 4) {
			int cdx = dx[d] + cx;
			int cdy = dy[d] + cy;
			if (cdx == nx && cdy == ny) {
				ans[2 * cx + dx[d]][2 * cy + dy[d]] = '.';
			}
		}
	}
	vector<vector<bool>> exi(dh,vector<bool>(dw));
	queue<P> q;
	rep(i, vs.size()) {
		q.push(vs[i]);
		exi[vs[i].first][vs[i].second] = true;
	}
	while (!q.empty()) {
		P p = q.front(); q.pop();
		int x = p.first;
		int y = p.second;
		rep(d, 4) {
			int nx = x + dx[d];
			int ny = y + dy[d];
			if (nx >= 0 && ny >= 0 && nx < dh && ny < dw) {
				if (!exi[nx][ny]) {
					exi[nx][ny] = true;
					q.push({ nx,ny });
					ans[2 * x + dx[d]][2 * y + dy[d]] = '.';
				}
			}
		}
	}
	if (bs) {
		vector<string> cop(w);
		rep(i, w) {
			cop[i].resize(h);
			rep(j, h) {
				cop[i][j] = ans[j][i];
			}
		}
		swap(cop, ans);
		swap(h, w);
	}

	rep(i, h)cout << ans[i] << "\n";
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	//cout << fixed << setprecision(10);
	//init_f();
	//init();
	//expr();
	//int t; cin >> t; rep(i, t)
	solve();
	return 0;
}