#include<cstdio>
int main(void){int h,w,i,j;scanf("%d%d",&h,&w);while((h!=0)||(w!=0)){for(i=0;i<h;++i){for(j=0;j<w;++j){printf("%c",((j+i)%2)?'.':'#');}puts("");}puts("");scanf("%d%d",&h,&w);}return(0);}
