var input = require('fs').readFileSync('/dev/stdin', 'utf8');
let sp = input.split("\n");
for( let i = 0; sp[i] !== "0 0"; i++ ) {
  let hw = sp[i].split(" ").map(Number);
  let h = hw[0]; w = hw[1];
  for( let hh = 0; hh < h; hh++ ) {
    let row = "";
    let plus = hh % 2 === 0 ? 0 : 1;
    for( let ww = 0 + plus; ww < w + plus; ww++ ) {
      row += ww % 2 === 0 ? "#" : ".";
    }
    console.log(row);
  }
  console.log();
}