#include <stdio.h>
#include <algorithm>
 
using namespace std;
 
int main(){
    int H,W;
    while(true){
        scanf("%d %d",&H,&W);
        if(H == 0 && W == 0) break;
        for(int i = 0; i < H; i++){
            for(int j = 0; j < W; j++){
                if((i+j)%2 == 0) printf("#");
                else{
                    printf(".");
                }
            }
            printf("\n");
        }
        printf("\n");
    }
}
