def build_hash_table(board):
	"""builds a hash table of locations of all the starting letters"""
	
	hash_table = {}
	for row in range(len(board)):
		for col in range(len(board[0])):
			
			letter = board[row][col]
			if letter in hash_table:
				hash_table[letter].append((row, col))
			else:
				hash_table[letter] = [(row, col)]
				
	return hash_table