#include <bits/stdc++>
using namespace std;

int main(){
    int H,W;
    while(1) {
        cin >> H,W;
        if (H == 0 && W ==0 ) break;
        
        for (int i = 0;i<H;i++){
            for (int j = 0;j <W;j++){
                if ((i+j)%2 == 0) cout << "#";
                else cout << ".";
            }
        cout<<endl;
        }

        cout <<endl;
     }
}
