ALL, YES, NO, TIME = set(), set(), set(), set(),
for i in range(int(input())):
    ALL.add(i)
z = 1
TIME.update(input().split())
z = input()
while ("HELP" not in TIME):
    if z == 'YES':
        YES.update(TIME)
    else:
        NO.update(TIME)
    TIME = set()
    TIME.update(input().split())
    z = input()
print(YES)