'use strict';
const x = require('fs').readFileSync('/dev/stdin', 'utf8');
const lines = x.split(/\n/);

for (let i = 0; i < lines.length ; i++) {
  const arr = lines[i].split(/\s/).map(Number);
  if ((arr[0]===0)&&(arr[1]===0)) break;

  for (let i = 0; i < arr[0]; i++){
    if (i%2===0) {
      for (let j=0; j < arr[1]; j++){
        if (j%2===0) process.stdout.write('#');
        else process.stdout.write('.');
      }
      console.log();
    } else {
      for (let j=0; j < arr[1]; j++){
        if (j%2===0) process.stdout.write('.');
        else process.stdout.write('#');
      }
      console.log();
    }
  }
  console.log();
}


