#include <bits/stdc++.h>
using namespace std;

struct iofast_t {
    iofast_t() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} iofast;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return vector(arg, init);
    else return vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

template <typename Container>
auto distance(const Container &c, decltype(begin(c)) iter) {
    return distance(begin(c), iter);
}

template <typename RIter, typename Compare = less<typename iterator_traits<RIter>::value_type>>
auto isort(RIter first, RIter last, Compare comp = Compare()) {
    vector<int> i(distance(first, last));
    iota(begin(i), end(i), 0);
    sort(begin(i), end(i), [&](auto x, auto y) {
        return comp(*(first + x), *(first + y));
    });
    return i;
}

template <typename, template <typename> typename, typename = void_t<>>
struct detect : false_type {};
template <typename T, template <typename> typename Check>
struct detect<T, Check, void_t<Check<T>>> : true_type {};
template <typename T, template <typename> typename Check>
constexpr inline bool detect_v = detect<T, Check>::value;

template <typename T>
using has_member_sort = decltype(declval<T>().sort());

template <typename Container, typename Compare = less<typename Container::value_type>>
auto sorted(Container c, Compare comp = Compare()) {
    if constexpr (detect_v<Container, has_member_sort>) {
        c.sort(comp);
        return c;
    }
    else {
        sort(begin(c), end(c), comp);
        return c;
    }
}

template <typename Container, typename Compare = equal_to<typename Container::value_type>>
auto uniqued(Container c, Compare comp = Compare()) {
    c.erase(unique(begin(c), end(c), comp), end(c));
    return c;
}

template <typename T, typename Compare = less<T>>
T &chmin(T &l, T r, Compare &&f = less<T>()) { return l = min(l, r, f); }
template <typename T, typename Compare = less<T>>
T &chmax(T &l, T r, Compare &&f = less<T>()) { return l = max(l, r, f); }

template <typename F>
constexpr auto fix(F &&f) noexcept {
    return [f = std::tuple<F>(std::forward<F>(f))](auto &&...args) mutable {
        return std::get<0>(f)(fix(std::get<0>(f)), std::forward<decltype(args)>(args)...);
    };
}

#include <atcoder/dsu>

int main() {
    constexpr int step[4][2] = {
        { 1, 0 }, { 0, 1 }, { -1, 0 }, { 0, -1 }
    };

    int h, w, x; cin >> h >> w >> x;

    if (x < h + w - 2 || x % 4 != (h + w - 2) % 4) {
        cout << -1 << endl;
        return 0;
    }

    const int max = [&]() {
        const int p = (h + 1) / 2 * (w + 1) / 2;
        if (h % 4 == 3 && w % 4 == 3) {
            return (p - 1) * 2 - 1;
        }
        return p * 2 - 1;
    }();

    if (max <= x) {
        cout << -1 << endl;
        return 0;
    }

    auto path = fix([](auto path, int h, int w, int x) -> vector<tuple<int, int>> {
        if (h % 2 == 0 && w % 2 != 0) {
            auto f = path(w, h, x);
            for (auto &[y, x] : f) {
                swap(y, x);
            }
            return f;
        }

        auto max_path = [](int h, int w) -> vector<tuple<int, int>> {
            auto p = vec(make_tuple(0, 0), 0);

            for (int i = 0; i < h - (h % 2 == 0) * 2; ++i) {
                for (int j = 0; j < w; ++j) {
                    if (i % 2 == 0) {
                        p.emplace_back(i, j);
                    }
                    if (i % 2 == 1) {
                        p.emplace_back(i, w - j - 1);
                    }
                }                    
            }

            if (h % 2 == 1) {
                return p;
            }
            p.emplace_back(h - 2, 0);

            for (int i = 1; i < w; ++i) {
                for (int j = 0; j < 2; ++j) {
                    if (i % 2 == 0) {
                        p.emplace_back(h - 1 - j, i);
                    }
                    if (i % 2 == 1) {
                        p.emplace_back(h - 2 + j, i);
                    }
                }
            }

            return p;
        };

        auto f = max_path(h, w);
        auto g = vec(make_tuple(0, 0), 0);
        auto vis = vec<bool>(false, h, w);

        int ly = -1, lx = -1;
        for (auto [fy, fx] : f) {
            int d = h + w - 2 - fy - fx;

            g.emplace_back(fy, fx);
            vis[fy][fx] = true;
            if (x == d) {
                tie(ly, lx) = { fy, fx };
                break;
            }

            --x;
        }

        if (ly + 1 < h && !vis[ly + 1][lx]) {
            while (ly + 1 < h) {
                g.emplace_back(++ly, lx);
            }
        }
        if (lx + 1 < w && !vis[ly][lx + 1]) {
            while (lx + 1 < w) {
                g.emplace_back(ly, ++lx);
            }
        }

        while (ly + 1 < h) {
            g.emplace_back(++ly, lx);
        }
        while (lx + 1 < w) {
            g.emplace_back(ly, ++lx);
        }

        return g;
    });

    atcoder::dsu dsu(h * w);

    auto ans = vec(string(w, '#'), h);
    auto p = path((h + 1) / 2, (w + 1) / 2, x / 2);

    int py = -1, px = -1;
    for (auto [y, x] : p) {
        y *= 2; x *= 2;

        ans[y][x] = '.';
        dsu.merge(0, y * w + x);
        if (0 <= min(py, px)) {
            int dy = (y - py) / 2, dx = (x - px) / 2;
            int ny = py + dy, nx = px + dx;
            ans[ny][nx] = '.';
            dsu.merge(0, ny * w + nx);
        }

        tie(py, px) = { y, x };
    }

    for (int i = 0; i < h; i += 2) {
        for (int j = 0; j < w; j += 2) {
            ans[i][j] = '.';

            for (auto [dy, dx] : step) {
                int ny = i + dy * 2, nx = j + dx * 2;

                if (min(ny, nx) < 0 || h <= ny || w <= nx) {
                    continue;
                }

                if (!dsu.same(i * w + j, ny * w + nx)) {
                    dsu.merge(i * w + j, ny * w + nx);
                    ans[ny][nx] = ans[ny - dy][nx - dx] = '.';
                }
            }
        }
    }

    for (auto &s : ans) {
        cout << s << '\n';
    }
    cout << flush;
}