#include<stdio.h>
int main(void){
	int i,j,H,W,count;
	while(1){
		scanf("%d %d",&H,&W);
		count = 0;
		j = 0;
		if(H==0 && W == 0) break;
		else if(H ==0 || W == 0) printf("\n");
		else {
			for(i=0;i<H;i++){
				count = i % 2;
				if(count == 0){
					while(1){
						printf("#");
						j++;
						if(j == W) break;
						printf(".");
						j++;
						if(j == W) break;
					}
				}
				else{
					while(1){
						printf(".");
						j++;
						if(j == W) break;
						printf("#");
						j++;
						if(j == W) break; 
					}
				}
				printf("\n");
		}
	printf("\n");
	}
	return 0;
}