#include<bits/stdc++.h>

using namespace std;

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