#include <stdio.h>

main(void)
{
	int H,W,a,b;
	
	while(1){
		scanf("%d%d",&H,&W);
		
		if(H==0 && W==0) break;
		
		for(a=1;a<=H/2;a++){
			for(b=1;b<=W/2;b++){
				if(a%2==1) printf("#.");
				
				else if(a%2==0) printf(".#");
			}
			printf("\n");
		}
		printf("\n");
	}
	return 0;
}
	