N = int(raw_input())
nonum=[]
ans=[]

taro = []
for i in range(N):
    taro.append(0)
for i in range(N):
    taro[i]=raw_input()

for i in range(N):
    if taro[i][8:10] == "NO":
        for j in range(0,7,2):
            if taro[i][j] not in nonum:
                nonum.append(taro[i][j])
            else:
                pass
    else:
        ans.append(taro[i][:7])
for i in range(10):
    i = str(i)
    if i in nonum:
        continue
    else:
        if ans == []:
            answer = i
            break
        else:
            pass
        
        for j in range(len(ans)):
            if i not in ans[j]:
                break
            else:
                answer = i
                continue

print answer