import std.stdio, std.conv, std.functional, std.string;
import std.algorithm, std.array, std.container, std.range, std.typecons;
import std.bigint, std.numeric, std.math, std.random;
import core.bitop;

string FMT_F = "%.10f";

static File _f;
void file_io(string fn) { _f = File(fn, "r"); }
static string[] s_rd;
T _RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T _RD(T = long)(File f) { while(!s_rd.length) s_rd = f.readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T[] _RDA(T = long)(T fix = 0) { auto r = readln.chomp.split.to!(T[]); r[] += fix; return r; }
T[] _RDA(T = long)(File f, T fix = 0) { auto r = f.readln.chomp.split.to!(T[]); r[] += fix; return r; }
T RD(T = long)() { if (_f.isOpen) return _RD!T(_f); else return _RD!T; }
T[] RDA(T = long)(T fix = 0) { if (_f.isOpen)  return _RDA!T(_f, fix); else return _RDA!T(fix); }

size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

void chmin(T)(ref T x, T y) { x = min(x, y); } void chmax(T)(ref T x, T y) { x = max(x, y); }
bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
T lcm(T)(T x, T y) { return x * (y / gcd(x, y)); }

long mod = 10^^9 + 7;
//long mod = 998_244_353;
//long mod = 1_000_003;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }
void modpow(ref long x, long y) { if (!y) { x = 1; return; } auto t = x; x.modpow(y>>1); x.modm(x); if (y&1) x.modm(t); }
void modd(ref long x, long y) { y.modpow(mod - 2); x.modm(y); }

void main()
{
	auto H = RD;
	auto W = RD;
	auto X = RD;

	bool isRotated;
	if (H / 2 % 2 == 1 && W / 2 % 2 == 0)
	{
		swap(H, W);
		isRotated = true;
	}
	else if (H / 2 % 2 == W / 2 % 2 && H < W)
	{
		swap(H, W);
		isRotated = true;
	}
	auto rem = X - (H+W-2);
	auto rt = H / 4;
	auto cnt = rt * (W-1) * 2;
	if (rem < 0 || rem % 4 || rem > cnt)
		writeln(-1);
	else
	{
		auto ans = new char[][](H, W);
		foreach (i; 0..H)
		{
			foreach (j; 0..W)
			{
				if (i % 2 == 1 && j % 2 == 1)
					ans[i][j] = '#';
				else
					ans[i][j] = '.';
			}
		}
		foreach (i; 0..W-1)
			ans[1][i] = '#';
		long y = 3;
		while (rem != 0)
		{
			auto c = min(W-1, rem / 4 * 2);
			auto l = W - c;
			rem -= c * 2;
			foreach (i; l+1..W)
				ans[y][i] = '#';
			if (rem != 0 && y+2 < H)
				foreach (i; l..W-1)
					ans[y+2][i] = '#';
			if (rem == 0)
			{
				foreach (i; 0..l)
				{
					if (i % 2 == 1)
					{
						ans[y+1][i] = '#';
						if (y+3 < H)
							ans[y+3][i] = '#';
					}
				}
				y += 3;
				break;
			}
			y += 4;
		}
		foreach (i; y..H)
		{
			foreach (j; 0..W)
			{
				if (j % 2)
					ans[i][j] = '#';
			}
		}
		if (isRotated)
		{
			foreach (j; 0..W)
			{
				foreach (i; 0..H)
				{
					write(ans[i][j]);
				}
				writeln;
			}
		}
		else
		{
			foreach (i; 0..H)
				writeln(ans[i]);
		}
	}

	stdout.flush;
	debug readln;
}