N = int(input()) counts = {} # S:C # 或使用 counts = defaultdict(int) 设定默认值为0 for _ in range(N): S, C = input().split() prefix = S[:2] if not counts.get((prefix, C)): counts[(prefix, C)] = 0 counts[(prefix, C)] += 1 res = 0 for (s1, s2) in counts.keys(): # s1!=s2即可保证A,B来自不同的州 if s1 < s2 and (s2, s1) in counts: res += counts[(s1, s2)] * counts[(s2, s1)] print(res)