# 1220. Count Vowels Permutation class Solution(object): def countVowelPermutation(self, n): a, e, i, o, u = 1, 1, 1, 1, 1 for _ in range(n - 1): a, e, i, o, u = e + i + u, a + i, e + o, i, i + o return (a + e + i + o + u) % (10**9 + 7) if __name__ == "__main__": obj = Solution() print(obj.countVowelPermutation(1)) # expect: 5 print(obj.countVowelPermutation(2)) # expect: 10 print(obj.countVowelPermutation(5)) # expect: 68