#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using VI = vector<int>;
using VL = vector<ll>;
using VS = vector<string>;
template<class T> using PQ = priority_queue<T, vector<T>, greater<T>>;
using graph = vector<VI>;
template<class T = ll> using w_graph = vector<vector<pair<int, T>>>;
#define FOR(i,a,n) for(int i=(a);i<(n);++i)
#define eFOR(i,a,n) for(int i=(a);i<=(n);++i)
#define rFOR(i,a,n) for(int i=(n)-1;i>=(a);--i)
#define erFOR(i,a,n) for(int i=(n);i>=(a);--i)
#define SORT(a) sort(a.begin(),a.end())
#define rSORT(a) sort(a.rbegin(),a.rend())
#define fSORT(a,f) sort(a.begin(),a.end(),f)
#define all(a) a.begin(),a.end()
#define out(y,x) ((y)<0||h<=(y)||(x)<0||w<=(x))
#define tp(a,i) get<i>(a)
#ifdef _DEBUG
#define line cout << "-----------------------------\n"
#define stop system("pause")
#endif
constexpr ll INF = 1000000000;
constexpr ll LLINF = 1LL << 60;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr ld eps = 1e-10;
constexpr ld pi = 3.1415926535897932;
template<class T>inline bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; }return false; }
template<class T>inline bool chmin(T& a, const T& b) { if (a > b) { a = b; return true; }return false; }
inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); }
template<class T>inline istream& operator>>(istream& is, vector<T>& v) { for (auto& a : v)is >> a; return is; }
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template<class T>inline vector<T> vec(size_t a) { return vector<T>(a); }
template<class T>inline vector<T> defvec(T def, size_t a) { return vector<T>(a, def); }
template<class T, class... Ts>inline auto vec(size_t a, Ts... ts) { return vector<decltype(vec<T>(ts...))>(a, vec<T>(ts...)); }
template<class T, class... Ts>inline auto defvec(T def, size_t a, Ts... ts) { return vector<decltype(defvec<T>(def, ts...))>(a, defvec<T>(def, ts...)); }
template<class T>inline void print(const T& a) { cout << a << "\n"; }
template<class T, class... Ts>inline void print(const T& a, const Ts&... ts) { cout << a << " "; print(ts...); }
template<class T>inline void print(const vector<T>& v) { for (int i = 0; i < v.size(); ++i)cout << v[i] << (i == v.size() - 1 ? "\n" : " "); }
template<class T>inline void print(const vector<vector<T>>& v) { for (auto& a : v)print(a); }
inline string reversed(const string& s) { string t = s; reverse(all(t)); return t; }
template<class T>inline T sum(const vector<T>& a, int l, int r) { return a[r] - (l == 0 ? 0 : a[l - 1]); }
template<class T>inline void END(T s) { print(s); exit(0); }
void END() { exit(0); }

bool solve(int h, int w, int d, VS& s) {
    s = VS(h, string(w, '#'));
    FOR(i, 0, h - 1)FOR(j, 0, w)if (i % 2 == 0 && j % 2 == 0)s[i][j] = '.';
    s[h - 1] = string(w, '.');

    auto v = vec<bool>(h, w);

    int y = 0, x = 0;
    bool r = 1;
    if ((h - 1 - y) + (w - 1 - x) > d)return false;
    while ((h - 1 - y) + (w - 1 - x) <= d) {
        v[y][x] = true;
        if (y == h - 1 && x == w - 1) {
            if (d > 0)return false;
            else break;
        }
        if (r) {
            if (x == w - 1) {
                s[y + 1][x] = '.';
                y += 2;
                r ^= 1;
            }
            else {
                s[y][x + 1] = '.';
                x += 2;
            }
        }
        else {
            if (x == 0) {
                s[y + 1][x] = '.';
                y += 2;
                r ^= 1;
            }
            else {
                if ((h - 1 - y) + (w - 1 - (x - 2)) > d - 2) {
                    s[y + 1][x] = '.';
                    y += 2;
                    v[y][x] = true;
                    while (x < w - 1) {
                        s[y][x + 1] = '.';
                        x += 2;
                        v[y][x] = true;
                    }
                    while (y < h - 1) {
                        s[y + 1][x] = '.';
                        y += 2;
                        v[y][x] = true;
                    }
                    break;
                }
                s[y][x - 1] = '.';
                x -= 2;
            }
        }
        d -= 2;
    }
    for (int j = 0; j < w - 1; j += 2) {
        int y = h - 1;
        while (!v[y - 2][j]) {
            s[y - 1][j] = '.';
            y -= 2;
        }
    }
    return true;
}

uint32_t rnd() {
    static uint32_t val = 2718281828ul;
    val ^= val << 13;
    val ^= val >> 17;
    val ^= val << 15;
    return val;
}

uint32_t rnd(uint32_t max) {
    return rnd() % max;
}

int main() {
    init();

    int t = 1;
    while (t--) {
        int h, w, d; cin >> h >> w >> d;
        //int h = rnd(10) * 2 + 3;
        //int w = rnd(10) * 2 + 3;
        //int d = 2 + rnd(h * w) / 2 * 2;
        print(h, w, d);
        if (d & 1) {
            print(-1);
        }
        if ((h / 2 + w / 2) % 2 != d / 2 % 2) {
            print(-1);
        }
        else {
            VS s;
            if (solve(h, w, d, s)) {
                FOR(i, 0, h)print(s[i]);
            }
            else if (solve(w, h, d, s)) {
                FOR(i, 0, h) {
                    FOR(j, 0, w)cout << s[j][i];
                    cout << "\n";
                }
            }
            else print(-1);
        }
    }

    return 0;
}