#include <math.h>
#include <iostream>
#include <algorithm>

using namespace std;

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