N = input()

nList = []
yList = []
r = ['0','1','2','3','4','5','6','7','8','9']

for i in range(int(N)):
    L = list(input().split())
    if 'NO' in L:
        nList.extend(L)
    else:
        yList.extend(L)
for n in nList:
    if n in r:
        r.remove(n)

if len(r) == 1:
    print(r[0])
else:
    wList = [x for x in set(r) if yList.count(x) > 1]
    for w in wList:
        if w in r:
            print(w)