#include<iostream>
using namespace std;

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