#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

/**
 * @brief https://tkmst201.github.io/Library/DataStructure/UnionFind.hpp
 */
struct UnionFind {
	using size_type = std::size_t;
	
private:
	size_type n;
	std::vector<int> dat;
	
public:
	explicit UnionFind(size_type n) : n(n), dat(n, -1) {}
	
	size_type size(size_type x) noexcept {
		assert(x < n);
		return -dat[find(x)];
	}
	
	size_type find(size_type x) noexcept {
		assert(x < n);
		if (dat[x] < 0) return x;
		return dat[x] = find(dat[x]);
	}
	
	void unite(size_type x, size_type y) noexcept {
		assert(x < n);
		assert(y < n);
		x = find(x);
		y = find(y);
		if (x == y) return;
		if (dat[x] < dat[y]) std::swap(x, y);
		dat[y] += dat[x];
		dat[x] = y;
	}
	
	bool issame(size_type x, size_type y) noexcept {
		assert(x < n);
		assert(y < n);
		return find(x) == find(y);
	}
};

int main() {
	int H, W, X;
	cin >> H >> W >> X;
	int h = (H + 1) / 2, w = (W + 1) / 2;
	if (X % 2 == 1 || (h + w) % 2 != X / 2 % 2) { puts("-1"); return 0; }
	X /= 2;
	
	bool trans = false;
	if (h % 2 == 0) {
		trans = true;
		swap(H, W);
		swap(h, w);
	}
	
	constexpr int dx[] {-1,0,1,0}, dy[] {0,-1,0,1}; // lurd ^1 で転置
	vector<int> dirs;
	
	// (h, w) = (odd, even) or (even, even)
	if (h + w - 2 > X || h * w - 1 < X || ((~(h | w) & 1) && h * w - 1 == X)) { puts("-1"); return 0; } 
	
	X -= h + w - 2;
	REP(i, (h - 1) / 2) {
		// rrr d lll d
		const int cur = min(X / 2, w - 1);
		REP(j, cur) dirs.emplace_back(2);
		dirs.emplace_back(3);
		REP(j, cur) dirs.emplace_back(0);
		dirs.emplace_back(3);
		X -= cur * 2;
	}
	if (h & 1) REP(i, w - 1) dirs.emplace_back(2); // r
	else {
		REP(i, X / 2) {
			dirs.emplace_back(3); // d
			dirs.emplace_back(2); // r
			dirs.emplace_back(1); // u
		}
		REP(i, w - 1 - X / 2) dirs.emplace_back(2); // r
		dirs.emplace_back(3); // d
	}
	
	if (trans) {
		for (int & a : dirs) a ^= 1;
		swap(H, W);
		swap(h, w);
	}
	vector<string> ans(H, string(W, '#'));
	REP(i, h) REP(j, w) ans[i << 1][j << 1] = '.';
	vector done(H, vector<int>(W));
	done[0][0] = true;
	int y = 0, x = 0;
	for (int dir : dirs) {
		const int ny = y + dy[dir], nx = x + dx[dir];
		ans[ny][nx] = '.';
		done[ny][nx] = true;
		y += 2 * dy[dir];
		x += 2 * dx[dir];
		done[y][x] = true;
	}
	
	REP(i, H) REP(j, W) {
		REP(dir, 4) {
			int ny = i + 2 * dy[dir], nx = j + 2 * dx[dir];
			if (ny < 0 || ny >= H || nx < 0 || nx >= W) continue;
			if (ans[i][j] == '#' || ans[ny][nx] == '#') continue;
			if (done[ny][nx]) continue;
			done[ny][nx] = true;
			done[i + dy[dir]][j + dx[dir]] = true;
			ans[i + dy[dir]][j + dx[dir]] = '.';
		}
	}
	
	REP(i, H) cout << ans[i] << '\n';
}