#include<iostream>
using namespace std;
int main(){
int H,W;

while(1){
cin >> H >> W;
if(H==0&&W==0)break;
for(int i=1;i<=H;i++){
for(int j=1;j<=W;j++){if((i+j)%2==1){cout << ".";}else{cout << "#";}
}
cout << "\n";
}
cout << endl;
}



return 0;
}
