import java.util.Scanner;
public class Main{
	public static void main(String[] args) {
		Scanner x = new Scanner(System.in);
		int h = x.nextInt();
		int w = x.nextInt();
		StringBuilder sb1 = new StringBuilder();
		while(h != 0 || w != 0){
		for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		}
		sb1.append("\n");
		h = x.nextInt();
		w = x.nextInt();
		}
		System.out.print(sb1);
	}

} import java.util.Scanner; Scanner java.util public class Main{
	public static void main(String[] args) {
		Scanner x = new Scanner(System.in);
		int h = x.nextInt();
		int w = x.nextInt();
		StringBuilder sb1 = new StringBuilder();
		while(h != 0 || w != 0){
		for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		}
		sb1.append("\n");
		h = x.nextInt();
		w = x.nextInt();
		}
		System.out.print(sb1);
	}

} Main public static void main(String[] args) {
		Scanner x = new Scanner(System.in);
		int h = x.nextInt();
		int w = x.nextInt();
		StringBuilder sb1 = new StringBuilder();
		while(h != 0 || w != 0){
		for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		}
		sb1.append("\n");
		h = x.nextInt();
		w = x.nextInt();
		}
		System.out.print(sb1);
	} main {
		Scanner x = new Scanner(System.in);
		int h = x.nextInt();
		int w = x.nextInt();
		StringBuilder sb1 = new StringBuilder();
		while(h != 0 || w != 0){
		for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		}
		sb1.append("\n");
		h = x.nextInt();
		w = x.nextInt();
		}
		System.out.print(sb1);
	} Scanner x = new Scanner(System.in); x new Scanner(System.in) int h = x.nextInt(); h x.nextInt() x.nextInt x int w = x.nextInt(); w x.nextInt() x.nextInt x StringBuilder sb1 = new StringBuilder(); sb1 new StringBuilder() while(h != 0 || w != 0){
		for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		}
		sb1.append("\n");
		h = x.nextInt();
		w = x.nextInt();
		} h != 0 || w != 0 h != 0 h 0 w != 0 w 0 {
		for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		}
		sb1.append("\n");
		h = x.nextInt();
		w = x.nextInt();
		} for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		} int i = 1 ; int i = 1 ; i 1 i <= h i h i++ i++ i {
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		} {
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		} if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			} i%2 != 0 i%2 i 2 0 {
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			} for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				} int n = 1 ; int n = 1 ; n 1 n <= w n w n++ n++ n {
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				} {
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				} if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					} n%2 != 0 n%2 n 2 0 {
						sb1.append("#");
					} sb1.append("#") sb1.append sb1 "#" {
						sb1.append(".");
					} sb1.append(".") sb1.append sb1 "." if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			} i%2 == 0 i%2 i 2 0 {
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			} for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				} int n = 1 ; int n = 1 ; n 1 n <= w n w n++ n++ n {
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				} {
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				} if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				} n%2 == 0 n%2 n 2 0 {
					sb1.append("#");
				} sb1.append("#") sb1.append sb1 "#" {
					sb1.append(".");
				} sb1.append(".") sb1.append sb1 "." sb1.append("\n") sb1.append sb1 "\n" sb1.append("\n") sb1.append sb1 "\n" h = x.nextInt() h x.nextInt() x.nextInt x w = x.nextInt() w x.nextInt() x.nextInt x System.out.print(sb1) System.out.print System.out System System.out sb1 String[] args args public class Main{
	public static void main(String[] args) {
		Scanner x = new Scanner(System.in);
		int h = x.nextInt();
		int w = x.nextInt();
		StringBuilder sb1 = new StringBuilder();
		while(h != 0 || w != 0){
		for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		}
		sb1.append("\n");
		h = x.nextInt();
		w = x.nextInt();
		}
		System.out.print(sb1);
	}

} public class Main{
	public static void main(String[] args) {
		Scanner x = new Scanner(System.in);
		int h = x.nextInt();
		int w = x.nextInt();
		StringBuilder sb1 = new StringBuilder();
		while(h != 0 || w != 0){
		for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		}
		sb1.append("\n");
		h = x.nextInt();
		w = x.nextInt();
		}
		System.out.print(sb1);
	}

} Main
import java.util.Scanner;
public class Main{
	public static void main(String[] args) {
		Scanner x = new Scanner(System.in);
		int h = x.nextInt();
		int w = x.nextInt();
		StringBuilder sb1 = new StringBuilder();
		while(h != 0 || w != 0){
		for(int i = 1 ; i <= h ; i++){
			if(i%2 != 0){
				for(int n = 1 ; n <= w ; n++){
					if(n%2 != 0 ){
						sb1.append("#");
					}else{
						sb1.append(".");
					}
				}
			}
			if(i%2 == 0){
				for(int n = 1 ; n <= w ; n++){
				if(n%2 == 0 ){
					sb1.append("#");
				}else{
					sb1.append(".");
				}
				}
			}
			sb1.append("\n");
		}
		sb1.append("\n");
		h = x.nextInt();
		w = x.nextInt();
		}
		System.out.print(sb1);
	}

}