#include <bits/stdc++.h>
#include <random>
#include <chrono>
using namespace std; typedef unsigned long long _ulong; typedef long long int lint; typedef long double ld; typedef pair<lint, lint> plint; typedef pair<ld, ld> pld;
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define FOR(i, begin, end) for(lint i=(begin),i##_end_=(end);i<i##_end_;++i)
#define IFOR(i, begin, end) for(lint i=(end)-1,i##_begin_=(begin);i>=i##_begin_;--i)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define endk '\n'
#define fi first
#define se second
struct fast_ios { fast_ios() { cin.tie(nullptr), ios::sync_with_stdio(false), cout << fixed << setprecision(20); }; } fast_ios_;
template<class T> auto add = [](T a, T b) -> T { return a + b; };
template<class T> auto f_max = [](T a, T b) -> T { return max(a, b); };
template<class T> auto f_min = [](T a, T b) -> T { return min(a, b); };
template<class T> using V = vector<T>;
using Vl = V<lint>; using VVl = V<Vl>;
template< typename T > ostream& operator<<(ostream& os, const vector< T >& v) {
    for (int i = 0; i < (int)v.size(); i++) os << v[i] << (i + 1 != v.size() ? " " : "");
    return os;
}
template< typename T >istream& operator>>(istream& is, vector< T >& v) {
    for (T& in : v) is >> in;
    return is;
}
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
lint gcd(lint a, lint b) { if (b == 0) return a; else return gcd(b, a % b); }
lint ceil(lint a, lint b) { return (a + b - 1) / b; }
lint digit(lint a) { return (lint)log10(a); }
lint e_dist(plint a, plint b) { return abs(a.fi - b.fi) * abs(a.fi - b.fi) + abs(a.se - b.se) * abs(a.se - b.se); }
lint m_dist(plint a, plint b) { return abs(a.fi - b.fi) + abs(a.se - b.se); }
bool check_overflow(lint a, lint b, lint limit) { return a > limit / b; } // a * b > c => true
void Worshall_Floyd(VVl& g) { REP(k, SZ(g)) REP(i, SZ(g)) REP(j, SZ(g)) chmin(g[i][j], g[i][k] + g[k][j]); }
const lint MOD1000000007 = 1000000007, MOD998244353 = 998244353, INF = 5e18;
lint dx[8] = { 1, 0, -1, 0, 1, -1, 1, -1 }, dy[8] = { 0, 1, 0, -1, -1, -1, 1, 1 };
bool YN(bool flag) { cout << (flag ? "YES" : "NO") << endk; return flag; } bool yn(bool flag) { cout << (flag ? "Yes" : "No") << endk; return flag; }
struct Edge {
    lint from, to;
    lint cost;
    Edge() {

    }
    Edge(lint u, lint v, lint c) {
        cost = c;
        from = u;
        to = v;
    }
    bool operator<(const Edge& e) const {
        return cost < e.cost;
    }
};
struct WeightedEdge {
    lint to;
    lint cost;
    WeightedEdge(lint v, lint c = 1) {
        to = v;
        cost = c;
    }
    bool operator<(const WeightedEdge& e) const {
        return cost < e.cost;
    }
};
using WeightedGraph = V<V<WeightedEdge>>;
typedef pair<plint, lint> tlint;
typedef pair<plint, plint> qlint;
typedef pair<char, lint> valchar;

lint H, W, X;
int main() {
    cin >> H >> W >> X;
    lint rev = 0;
    if (H > W) {
        swap(H, W);
        rev = 1;
    }
    if (H + W - 2 > X) {
        cout << -1 << endk;
        return 0;
    }
    lint curr_score = H + W - 2 + (W - 1) * ((H - 1) / 4) * 2;
    if (curr_score < X) {
        cout << -1 << endk;
        return 0;
    }
    if ((H + W) % 2 != X % 2) {
        cout << -1 << endk;
        return 0;
    }

    V<string> ans(H);
    REP(i, H) {
        string str = "";
        REP(j, W) str += ".";
        ans[i] = str;
    }
    REP(i, H) {
        if (i % 2 == 0) continue;
        if ((i / 2) % 2 == 0) {
            REP(j, W - 1) ans[i][j] = '#';
        }
        else {
            REP(j, W - 1) ans[i][j + 1] = '#';
        }
    }
    REP(i, H) {
        if (i % 2 == 0) continue;
        if ((i / 2) % 2 == 0) {
            IREP(j, W - 1){
                if (curr_score == X) break;
                ans[i][j] = '.';
                curr_score -= 2;
            }
        }
    }
    if (!rev) {
        REP(i, H) {
            cout << ans[i] << endk;
        }
    }
    else {
        REP(j, W) {
            REP(i, H) {
                cout << ans[i][j];
            }
            cout << endk;
        }
    }
}