#include<bits/stdc++.h>
using namespace std;
using ll=long long;


int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    ll H,W,K;
    cin>>H>>W>>K;
    if(K==0){
        for(int h=0;h<H;h++){
            cout<<string(W,'.')<<"\n";
        }
        return 0;
    }
    if(K<1){
        cout<<-1<<"\n";
    }
    assert(K<=H*W-H-W+2);
    cout<<-1<<"\n";
}