#include<stdio.h>
int main(){
    int H, W, i, j;
    while(1){
        scanf("%d%d", &H, &W);
        if(H == 0&&W == 0){break;}

        for(i = 0;i <= H;i++){
            for(j = 0;j <= W;j++){
                if(j%2 == 1){
                    if(i%2 == 1)
                    printf("#");
                    else
                    printf(".");
                }
                else{
                    if(i%2 == 1)
                    printf(".");
                    else
                    printf("#");
                }
            }
        printf("\n");
        }
    printf("\n")
    }
    return 0;
 }

