class Solution:

     def findJudge(self, N: int, trust: 'List[List[int]]') -> int:

         if N==1 and len(trust)==0:

             return 1

         s = list(range(1,N+1))

         d = {}

         for t in range(len(trust)):

             a1 = trust[t][0]

             a2 = trust[t][1]

             if a1 in s:

                 s.remove(a1)

             if a2 in d.keys():

                 d.update({a2:d[a2]+1})

             else:

                 d.update({a2:1})

         if len(s)==1 and s[0] in d.keys() and d[s[0]]==N-1:

             return s[0]

         else:

             return -1