#include<iostream>
using namespace std;
int main()
{
    int h,w;
    cin >> h >> w;
    while(h!=0&&w!=0)
    {
        for(int i=0;i<h;i+=1)
        {
            for(int j=0;j<w;j+=1)
            {
                if(i%2==j%2)
                {
                    cout << "#";
                }
                else
                {
                    cout <<".";
                }
            }
            cout << endl;
        }
        cin << h << w;
    }
}

