AtCoder Beginner Contest 151 C. Welcome to AtCoder【Python】

https://atcoder.jp/contests/abc151/tasks/abc151_c
AtCoder ProblemsのRecommendationで Difficulty: 333、Solve Probability: 52%でした。

N, M = map(int, input().split())
S = []
for i in range(N):
    S.append([])

for i in range(M):
    p, s = input().split()
    p = int(p)
    S[p-1].append(s)
ac_num = 0
pena_num = 0
for i in range(N):
    sum_wa = 0
    for j in S[i]:

        if j == 'WA':
            sum_wa += 1
        else:
            ac_num += 1
            pena_num += sum_wa
            break
print(ac_num, pena_num)

1度入力例2に引っかかってしまったのが反省点です。