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