#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
#define ll long long
#define GET_REP(_1, _2, _3, _4,NAME, ...) NAME
#define rep1(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i, m, n) for (int i = (n); i < (m); ++i)
#define rep3(i, m, n, o) for (int i = (n); i < (m); i+=o)
#define rep(...) GET_REP(__VA_ARGS__, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep1(i,n) for (int i = (n); i > 0; i--)
#define nall(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define fi first
#define se second
#define getvec(a,n,s) \
    vector<s> a(n);\
    for (auto& i:a) cin >>i;
#define int long long
#define vi vector<int>
#define vpii vector<pair<int,int>>
#define vs vector<string>
#define vvi vector<vector<int>>
#define vvs vector<vector<string>>

template <typename T>
    auto vec(size_t n, T val) {
    return std::vector<T>(n, val);
}
template <typename... Sizes>
    auto vec(size_t n, Sizes... sizes) {
    return std::vector<decltype(vec(sizes...))>(n, vec(sizes...));
}
random_device rd;
mt19937 gen(rd());
//uniform_int_distribution<int> dist();

signed main() {
    int h, w, k;
    cin >> h >> w >> k;

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

    vpii move = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
    vs s(h), t(h);
    rep(i, h) {
        s[i] = "";
        rep(j, w){
            s[i] += '.';
        }
        //cout << s[i] << endl;
    }
    t = s;

    pair<int, int> now = {0, 0};
    int bod = 0, mode = 0;

    while(true) {
        //cout << now.first << " " << now.second << endl;
        s[now.first][now.second] = '#';
        if((now.first == 0 && now.second == w - 1) || (now.first == h - 1 && now.second == 0) || (now.first == h - 1 && now.second == w - 1)) bod = bod;
        else if(now.first == 0 && now.second == 0) bod += 2;
        else if(now.first == 0 || now.first == h - 1 || now.second == 0 || now.second == w - 1) {
            //kabenotoki
            bod += 1;
        }
        else bod += 2;
        if(bod >= k) {
            if(bod > k) s[0][0] = '.';
            break;
        }

        bool ok = true;
        pair<int,int> next = {now.first + move[mode % 4].first, now.second + move[mode % 4].second};
        if(next.first < 0 || next.first > h - 1 || next.second < 0 || next.second > w - 1) ok = false;
        if(ok == true && t[next.first][next.second] == 'x') ok = false;
        if(ok == false) {
            next = now;
            mode++;
            next = {now.first + move[mode % 4].first, now.second + move[mode % 4].second};
        }

        rep(i, 4) {
            pair<int, int> ng;
            ng.first = now.first + move[i].first;
            ng.second = now.second + move[i].second;
            if(ng.first < 0 || ng.first > h - 1 || ng.second < 0 || ng.second > w - 1) continue;
            t[ng.first][ng.second] = 'x';
        }

        now.first = next.first;
        now.second = next.second;
    }

    rep(i, h) cout << s[i] << endl;
}