#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;
//---------------------------------//

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] = '.';
	int y = 0, x = 0;
	for (int dir : dirs) {
		ans[y + dy[dir]][x + dx[dir]] = '.';
		y += 2 * dy[dir];
		x += 2 * dx[dir];
	}
	REP(i, H) cout << ans[i] << '\n';
}