#include <bits/stdc++.h>
//#include <chrono>
#pragma GCC optimize("O3")
using namespace std;
#define reps(i,s,n) for(int i = s; i < n; i++)
#define rep(i,n) reps(i,0,n)
#define Rreps(i,n,e) for(int i = n - 1; i >= e; --i)
#define Rrep(i,n) Rreps(i,n,0)
#define ALL(a) a.begin(), a.end()

using ll = long long;
using vec = vector<ll>;
using mat = vector<vec>;

ll N,M,H,W,Q,K,A,B;
string S;
using P = pair<ll, ll>;
const ll INF = (1LL<<60);

template<class T> bool chmin(T &a, const T b){
    if(a > b) {a = b; return true;}
    else return false;
}
template<class T> bool chmax(T &a, const T b){
    if(a < b) {a = b; return true;}
    else return false;
}
template<class T> void my_printv(std::vector<T> v,bool endline = true){
    if(!v.empty()){
        for(std::size_t i{}; i<v.size()-1; ++i) std::cout<<v[i]<<" ";
        std::cout<<v.back();
    }
    if(endline) std::cout<<std::endl;
}

void no(){
    cout<<-1<<endl;
    exit(0);
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cin>>H>>W>>K;
    if(K&1) no();
    int h = (H+1)/2, w = (W+1)/2, r = K / 2, minr = h + w - 2;
    if(r < minr || h * w - 1 < r || (r&1) != (minr&1)) no();
    r -= minr;
    vector<string> ans(H, string(W, '.'));
    for(int j = 1; j < W; j += 2){
        reps(i, 1, H) ans[i][j] = '#';
    }
    int height = 1, pos = W - 3;
    while(r && height + 3 < H){
        ans[height][pos] = ans[height + 2][pos + 2] = '#';
        ans[height + 1][pos + 1] = ans[height + 3][pos + 1] = '.';
        if(pos == 0){
            height += 4;
            pos = W - 3;
        }else{
            pos -= 2;
        }
        r -= 2;
    }
    pos = 1;
    while(r){
        ans[H - 1][pos] = '.';
        ans[H - 3][pos] = '#';
        pos += 4;
        r -= 2;
    }

    rep(i, H) cout<<ans[i]<<endl;
}