N=int(input())
flag=["0","1","2","3","4","5","6","7","8","9"]
#print(flag[0])

for i in range(N):
    sug=input().split()
    if sug[4]=="YES":
        flag=list(set(flag)&set(sug))
    else:
        sug[4]!="YES"
        flag=list(set(flag)-set(sug))

print(int(flag[0]))