C :

int main(int argc, char* argv[])
{
	int n,m,i,j,count,k;
	char str;
	 while(~scanf("%d%d",&n,&m))
	 {
		 str='A';
	     for(i=0;i<n;i++)	     
		 {
            for(k=0;k<i;k++)
				printf("%c",str+i-k);
			 for(j=0;j<m-k;j++)
			 {  
				 printf("%c",str+j+i-k); 
			 }
			 puts("");
		 }
	 }
	return 0;
}

Java :

import java.util.Scanner;


public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args){
		int n,m;
		n=sc.nextInt();
		m=sc.nextInt();
		String map = "ZYXWVUTSRQPONMLKJIHGFEDCBABCDEFGHIJKLMNOPQRSTUVWXYZ";
		for (int i = 25; i > (25-n); i--) {
			System.out.println(map.substring(i, i+m));
		}
	}
}