import std.stdio;
import std.string;
import std.conv;
import std.algorithm;
import std.range;
import std.container;
import std.bigint;
import std.math;

void main()
{
	while (1) {
    auto x = readln.chomp.split.map!(to!int);
    if (x[0] == 0) break;
    foreach (i; 0..x[0]) {
      foreach (j; 0..x[1]) {
        if ((i+j)%2) write(".");
        else write("#");
      }
      writeln("");
    }
    writeln("");
  }
}