#include<iostream>
using namespace std;

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