const l=require("fs").readFileSync("/dev/stdin", "utf8").split("\n")
let i=0
while(true){
  let [h,w]=l[i++].split(" ").map(Number)
  if (!h&&!w)break
  let f=s=>`${(Array(w+1).join(s)).slice(0,w)}\n`
  let c=f("#.")
  console.log(`${`${c}${f(".#")}`.repeat(Math.floor(h/2))}${h%2!=0?c:""}`)
}
