#include "bits/stdc++.h"
//#include "atcoder/all"
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int H, W, X;
	cin >> H >> W >> X;
	if (X % 4 != ((H - 1) + (W - 1)) % 4) {
		cout << -1 << endl;
		return 0;
	}
	int min = H - 1 + W - 1;
	int max = ((H + 1) / 2 * (W + 1) / 2) * 2;
	if ((3 == H % 4) && (3 == W % 4)) {
		max -= 2;
	}
	if ((X < min) || (max < X)) {
		cout << -1 << endl;
		return 0;
	}
	bool cross = false;
	if ((3 == W % 4) || (3 != H % 3)) {
		swap(H, W);
		cross = true;
	}
	vector<string>S(H);
	rep(i, H) {
		rep(j, W) {
			if ((0 == j % 2) || (0 == i)) { S[i] += '.'; }
			else { S[i] += '#'; }
		}
	}
	int zan = (X - (H - 1) - (W - 1)) / 4;
	int max1line = (H - 1) / 2;
	rep(i, (W - 1) / 4) {
		if (zan > max1line) {
			S[0][4 * i + 1] = '#';
			S[max1line * 2][4 * i + 1] = '.';
			zan -= max1line;
		}
		else {
			S[0][4 * i + 1] = '#';
			S[zan * 2][4 * i + 1] = '.';
			zan = 0;
		}
	}
	rep(i, zan) {
		S[H - 2 - 4 * i][W - 1] = '#';
		S[H - 1 - 4 * i][W - 2] = '.';
		S[H - 3 - 4 * i][W - 2] = '.';
		S[H - 4 - 4 * i][W - 3] = '#';
	}
	if (cross) {
		rep(i, W) {
			rep(j, H) { cout << S[j][i]; }
			cout << endl;
		}
	}
	else {
		rep(i, H) { cout << S[i] << endl; }
	}

	return 0;
}