def add(S,N,k,i=0):
    if i == k:
        return S
    return add(S.union(N[i]),N,k,i+1)
def pull(S,N,k,i=1):
    if i == k:
        return S
    return pull(S.intersection(N[i]),N,k,i+1)
N = int(input())
A = [set(input().split(' ')) for i in range(N)]
NO = [i for i in A if "NO" in i]
YES  = [i for i in A if "YES" in i]
if YES:
    n = add(set(),NO,len(NO))
    r = pull(YES[0],YES,len(YES))
    r2 = r.difference(n.union({"YES",}))
    print(list(r2)[0])
else:
    n = add(set(),NO,len(NO))
    s = {'1','2','3','4','5','6','7','8','9'}
    print(list(s.difference(n))[0])