import std.stdio;
import std.array;
import std.conv;
import std.string;
import std.algorithm;

void main()
{
    string s;
    while( (s=readln.strip) != "0 0") {
        auto n = map!(to!int)(s.strip.split);
        int h = n[0], w = n[1];

        foreach(i;0..h) {
            foreach(j;0..w) {
              write((i+j)%2==0 ? '#':'.');
            }
            writeln();
        }
       writeln();
    }
}