#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long int ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vvvl> vvvvl;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef pair<ll,ll> pl;
typedef pair<ll,pl> ppl;
typedef pair<ll,ppl> pppl;
typedef pair<ll,pppl> pppppl;
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define all(a) begin(a),end(a)
#define sz(a) (int)(a).size()
// #define F first
// #define S second
#define bs(A,x) binary_search(all(A),x)
#define lb(A,x) (ll)(lower_bound(all(A),x)-A.begin())
#define ub(A,x) (ll)(upper_bound(all(A),x)-A.begin())
#define cou(A,x) (ll)(upper_bound(all(A),x)-lower_bound(all(A),x))
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
template<class T>bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T&a,T b){if(b<a){a=b;return 1;}return 0;}
//*
using mint=modint998244353;
const ll mod=998244353;
//*/
/*
using mint=modint1000000007;
const ll mod=1000000007;
//*/
//using mint=modint;
//*
typedef vector<mint> vm;
typedef vector<vm> vvm;
typedef vector<vvm> vvvm;
typedef vector<vvvm> vvvvm;
ostream&operator<<(ostream&os,mint a){os<<a.val();return os;}
istream&operator>>(istream&is,mint&a){int x;is>>x;a=mint(x);return is;}
//*/
template<typename T1,typename T2>ostream&operator<<(ostream&os,pair<T1,T2>p){os<<p.F<<" "<<p.S;return os;}
template<typename T1,typename T2>istream&operator>>(istream&is,pair<T1,T2>&p){is>>p.F>>p.S;return is;}
template<typename T>ostream&operator<<(ostream&os,vector<T>v){rep(i,0,sz(v))os<<v[i]<<(i+1!=sz(v)?" ":"");return os;}
template<typename T>istream&operator>>(istream&is,vector<T>&v){for(T&in:v)is>>in;return is;}

void Solve() {
    int N, M, K;
    cin >> N >> M >> K;
    if (N == 1 || M == 1) {
        if (K >= 2) {
            cout << -1 << endl;
            return;
        }
        vector<string> ANS(N, string(M,'.'));
        if (K == 1) ANS[0][0] = '#';
        rep(i,0,N) cout << ANS[i] << endl;
        return;
    }
    if (K == 0) {
        vector<string> ANS(N, string(M,'.'));
        rep(i,0,N) cout << ANS[i] << endl;
        return;
    }
    if (K == 1) {
        cout << -1 << endl;
        return;
    }
    if (K > N*M-N-M+2) {
        cout << -1 << endl;
        return;
    }
    if (N == 2 && M == 2) {
        assert(K==2);
        cout << "##" << endl;
        cout << ".." << endl;
        return;
    }
    bool flip = false;
    if (N > M) {
        swap(N,M);
        flip = true;
    }
    vector<string> ANS(N, string(M, '.'));
    rep(i,0,N) {
        ANS[i][0] = '.';
        ANS[i][M-1] = '#';
        rep(j,1,M-1) {
            if (i % 2 == 0) ANS[i][j] = '.';
            else ANS[i][j] = '#';
        }
    }
    int Cur = N*M-N-M+2;
    rep(i,0,N) {
        if (Cur == K) break;
        if (i % 2 == 1) continue;
        if (i == 0 || i == N-1) {
            rrep(j,1,M-1) {
                if (Cur == K) break;
                ANS[i][j] = '#';
                Cur--;
            }
            if (Cur == K) break;
            if (i == 0) {
                ANS[i][0] = ANS[i+1][0] = '#';
                Cur--;
            }
            if (i == N-1) {
                ANS[i][0] = '#';
                Cur-=2;
            }
        }
        else {
            rrep(j,1,M-1) {
                if (Cur == K) break;
                ANS[i-1][0] = '.';
                ANS[i][j] = '#';
                Cur--;
                if (Cur == K) break;
                ANS[i-1][0] = '#';
                Cur--;
            }
            if (Cur == K) break;
            ANS[i][0] = '#';
            Cur--;
            if (Cur == K) break;
            if (i + 1 < N) {
                ANS[i+1][0] = '#';
                Cur--;
            }
        }
    }
    assert(Cur == K);
    if (flip) {
        swap(N,M);
        vector<string> T(N, string(M,' '));
        rep(i,0,N) {
            rep(j,0,M) T[i][j] = ANS[j][i];
        }
        swap(ANS,T);
    }
    rep(i,0,N) cout << ANS[i] << endl;
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    ll _ = 1;
    //cin>>_;
    while(_--){
        Solve();
    }
    return 0;
}