text: # Problem Problem Desrcription Shil likes to play with trees a lot.He is playing with an undirected tree containing N nodes.He wants to find out total number of unordered triplets (A,B,C) such that A is not connected to B, B is not connected to C and A is not connected to C by a direct edge (No two of A, B, C are mutually connected).Since he doesn't like to play with this alone , he asks for your help.Input The first line of each test case contains a single integer N denoting the number of nodes.Next N - 1 lines consists of two integers u and v describing an edge from u to v Output Output a single line containing total number of triplets.Constraints 1 ≤ N ≤ 10^5 1 ≤ u, v ≤ N Example Input: 5 1 2 1 3 3 4 2 5 Output: 1 Explanation The only possible triplet is (1,4,5) # Solution N=int(input()) D=[0]*N for i in range(N-1): a,b=map(int,raw_input().split()) a-=1;b-=1; D[a]+=1 D[b]+=1 ans=N*(N-1)*(N-2) ans/=6 ans-=(N-1)*(N-2) for i in D: if i>=2: ans+=(i*(i-1))/2 print ans