n = int(input())
Q = [input().split() for i in range(n)]
for i in range(10):
    ans = str(i)
    ok = 1
    for q in Q:
        if q[-1] == "NO" and ans in q:
            ok = 0
        if q[-1] == "YES" and ans not in q:
            ok = 0
    if ok:
        print(ans)
        exit()