#include<stdio.h>

int main(void){
    int i,j,h,w,start,next;

    while(1){
        scanf("%d %d",&h,&w);
        if(h == 0 && w == 0)
            break;
        start = 1;
        for(i = 0;i < h;i++){
            next = start;
            for(j = 0;j < w;j++){
                if(next == 1)
                    printf("#");
                else
                    printf(".");
                next *= -1;
            }
            printf("\n");
            start *= -1;
        }
        printf("\n);
    }
    return 0;
}