function Main(input){
  const arr = input.split('\n');
  let data, row, col;
  let pA = '';
  let pB = '';

  for (let i = 0; i < arr.length; i++){
    data = arr[i].split(' ');
    row = Number(data[0]);
    col = Number(data[1]);

    if (row === 0 && col === 0){
      break;
    } else {
    for (let j = 1; j <= col; j++){
      if (j % 2 === 1){pA+='.'; pB+='#';} else { pA+='#'; pB+='.';}}
    for (let k = 1; k <= row ; k++){
        if (k % 2 === 1){console.log(pB);}else{console.log(pA);}}
        pA = '';
        pB = '';
        console.log();
        }
    }
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));
