n=int(input())
l=[]
s1=set()
s2=set()
for i in range(n):
    l+=[input().split()]
    if l[i][-1]=="NO":
        s1|=set(l[i])
    else:
        if len(s2)==0:
            s2=set(l[i])
        else:
            s2&=set(l[i])
if len(s2)==2:
    s2.remove("YES")

for i in range(10):
    if (str(i) not in s1) and (str(i) in s2):
        print(i)
        break