import sys
sys.setrecursionlimit(5000)

def write_answer(answer):
    with open(output_file, 'a') as file:
        file.write(answer+'\n')

# def remove_first_symbol_from_the_list():

def line_checking(row, position):
    help_row = row
    help_position = position
    next_character_array =[]
    bool_value = False
    for element in row:
        if element=='\n':
                if position in what_is_the_ended_positions():
                    return True
                else:
                    return False
        next_character_array = find_next_position(help_position, element)
        if next_character_array != []:
            if len(next_character_array)>1:
                for element_in_next_character_array in next_character_array:
                    if bool_value ==True:
                        break
                    else:
                        bool_value =line_checking(help_row[1:], element_in_next_character_array)
            else:
                # remove_first_symbol_from_the_list()
                help_row = help_row[1:]
                bool_value = line_checking(help_row, next_character_array[0])
        else:
            break
        return bool_value


def find_next_position(position, character):
    with open(used_table, 'r') as readed_used_table:
        take_all_possible_positions = []
        for row_used_table in readed_used_table:
            line = row_used_table.strip().split(' ')
            if len(line) != 1:
                if position == line[0] and character == line[2]:
                    take_all_possible_positions.append(line[1])

        return take_all_possible_positions
def what_is_the_ended_positions():
    array = []
    with open(used_table, 'r') as file:
        for row in file:
            line = row.strip().split('\t')
            if len(line)==1:
                array += line
        return array
used_table = 'test.arg'
input_file = 'test.in'
output_file = 'test.out'
# what_is_the_ended_positions()
with open(output_file, 'w') as readed_output_file:
    with open(input_file, 'r') as readed_input_file:
        for row_input_file in readed_input_file:
            if line_checking(row_input_file, '0')==True:
                write_answer('YES')
            else:
                write_answer('NO')