#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define drep(i,j,n) for(int i=0;i<(int)(n-1);i++)for(int j=i+1;j<(int)(n);j++)
#define trep(i,j,k,n) for(int i=0;i<(int)(n-2);i++)for(int j=i+1;j<(int)(n-1);j++)for(int k=j+1;k<(int)(n);k++)
#define codefor int test;scanf("%d",&test);while(test--)
#define INT(...) int __VA_ARGS__;in(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;in(__VA_ARGS__)
#define yes(ans) if(ans)printf("yes\n");else printf("no\n")
#define Yes(ans) if(ans)printf("Yes\n");else printf("No\n")
#define YES(ans) if(ans)printf("YES\n");else printf("NO\n")
#define vector2d(type,name,h,...) vector<vector<type>>name(h,vector<type>(__VA_ARGS__))
#define vector3d(type,name,h,w,...) vector<vector<vector<type>>>name(h,vector<vector<type>>(w,vector<type>(__VA_ARGS__)))
#define umap unordered_map
#define uset unordered_set
using namespace std;
using ll = long long;
const int MOD=1000000007;
const int MOD2=998244353;
const int INF=1<<30;
const ll INF2=(ll)1<<60;
//入力系
void scan(int& a){scanf("%d",&a);}
void scan(long long& a){scanf("%lld",&a);}
template<class T,class L>void scan(pair<T, L>& p){scan(p.first);scan(p.second);}
template<class T,class U,class V>void scan(tuple<T,U,V>& p){scan(get<0>(p));scan(get<1>(p));scan(get<2>(p));}
template<class T> void scan(T& a){cin>>a;}
template<class T> void scan(vector<T>& vec){for(auto&& it:vec)scan(it);}
void in(){}
template <class Head, class... Tail> void in(Head& head, Tail&... tail){scan(head);in(tail...);}
//出力系
void print(const int& a){printf("%d",a);}
void print(const long long& a){printf("%lld",a);}
void print(const double& a){printf("%.15lf",a);}
template<class T,class L>void print(const pair<T, L>& p){print(p.first);putchar(' ');print(p.second);}
template<class T> void print(const T& a){cout<<a;}
template<class T> void print(const vector<T>& vec){if(vec.empty())return;print(vec[0]);for(auto it=vec.begin();++it!= vec.end();){putchar(' ');print(*it);}}
void out(){putchar('\n');}
template<class T> void out(const T& t){print(t);putchar('\n');}
template <class Head, class... Tail> void out(const Head& head,const Tail&... tail){print(head);putchar(' ');out(tail...);}
//デバッグ系
template<class T> void dprint(const T& a){cerr<<a;}
template<class T> void dprint(const vector<T>& vec){if(vec.empty())return;cerr<<vec[0];for(auto it=vec.begin();++it!= vec.end();){cerr<<" "<<*it;}}
void debug(){cerr<<endl;}
template<class T> void debug(const T& t){dprint(t);cerr<<endl;}
template <class Head, class... Tail> void debug(const Head& head, const Tail&... tail){dprint(head);cerr<<" ";debug(tail...);}
ll intpow(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; }
ll modpow(ll a, ll b, ll p){ ll ans = 1; while(b){ if(b & 1) (ans *= a) %= p; (a *= a) %= p; b /= 2; } return ans; }
ll modinv(ll a, ll m) {ll b = m, u = 1, v = 0;while (b) {ll t = a / b;a -= t * b; swap(a, b);u -= t * v; swap(u, v);}u %= m;if (u < 0) u += m;return u;}
ll updivide(ll a,ll b){if(a%b==0) return a/b;else return (a/b)+1;}
template<class T> void chmax(T &a,const T b){if(b>a)a=b;}
template<class T> void chmin(T &a,const T b){if(b<a)a=b;}

int main(){
    INT(h,w,x);
    int xorigin=x;
    if(x<h+w-2||x%2!=0){
        out(-1);
        return 0;
    }
    vector2d(char,ans,h,w,'.');
    int cnt=(x-(h+w-2))/2;
    if(h%4==1){
        rep(y,h){
            if(y%2==0)continue;
            if(y%4==1){
                rep(x,w-1)ans[y][x]='#';
            }else if(y%4==3){
                int x=w-1;
                while(x&&cnt){
                    ans[y][x]='#';
                    x--;
                    cnt--;
                }
                if(!cnt){
                    while(x--){
                        ans[y][x]='#';
                    }
                }
            }
        }
    }else if(w%4==1){
        rep(x,w){
            if(x%2==0)continue;
            if(x%4==1){
                rep(y,h-1)ans[y][x]='#';
            }else if(x%4==3){
                int y=h-1;
                while(y&&cnt){
                    ans[y][x]='#';
                    y--;
                    cnt--;
                }
                if(!cnt){
                    while(y--){
                        ans[y][x]='#';
                    }
                }
            }
        }
    }else{
        rep(y,h){
            if(y%2==0)continue;
            if(y%4==1){
                rep(x,w-1)ans[y][x]='#';
            }else if(y%4==3){
                x=w-1;
                while(x&&cnt){
                    ans[y][x]='#';
                    x--;
                    cnt--;
                }
                if(!cnt){
                    while(x--){
                        ans[y][x]='#';
                    }
                }
            }
        }
        if(cnt>=1){
            cnt=(xorigin-(h+w-2))/2;
            rep(y,h)rep(x,w)ans[y][x]='.';
            rep(x,w){
                if(x%2==0)continue;
                if(x%4==1){
                    rep(y,h-1)ans[y][x]='#';
                }else if(x%4==3){
                    int y=h-1;
                    while(y&&cnt){
                        ans[y][x]='#';
                        y--;
                        cnt--;
                    }
                    if(!cnt){
                        while(y--){
                            ans[y][x]='#';
                        }
                    }
                }
            }
        }
        if(cnt>=1){
            if(h+w>=15){
                goto skip;
            }
            cnt=(xorigin-(h+w-2))/2;
            rep(y,h)rep(x,w)ans[y][x]='.';
            rep(x,w){
                if(x%2==0)continue;
                if(x%4==1){
                    rep(y,2)ans[y][x]='#';
                }else if(x%4==3){
                    int y=2;
                    while(y&&cnt){
                        ans[y][x]='#';
                        y--;
                        cnt--;
                    }
                    if(!cnt){
                        while(y--){
                            ans[y][x]='#';
                        }
                    }
                }
            }
            for(int y=3;y<h;y++){
                if(y%2==0)continue;
                if(y%4==3){
                    rep(x,w-1)ans[y][x]='#';
                }else if(y%4==1){
                    int x=w-1;
                    while(x&&cnt){
                        ans[y][x]='#';
                        x--;
                        cnt--;
                    }
                    if(!cnt){
                        while(x--){
                            ans[y][x]='#';
                        }
                    }
                }
            }
        }
    }
    skip:
    if(cnt>=1){
        out(-1);
        return 0;
    }
    rep(y,h){
        rep(x,w){
            cout<<ans[y][x];
        }
        cout<<endl;
    }
}