const input = require('fs').readFileSync('/dev/stdin', 'utf-8').trim();
const num_pairs = input.split(/\r?\n/).map(str => str.split(" ").map(n => Number(n)));

for (let l = 0; l < num_pairs.length; l++) {
  const H = num_pairs[l][0];
  const W = num_pairs[l][1];

  if (H === 0 && W === 0) break;

  for (let i = 0; i < H; i++) {
    for (let j = 0; j < W; j++) {
      if ( (i+j) % 2 === 0) {
        process.stdout.write("#");
      } else {
        process.stdout.write(".");
      }
    }
    console.log("");
  }
  console.log("");
}

