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