1225. Флаги

1225_flags.py

#!/usr/bin/python3


def get_combination_count(i):
    global arr
    if arr[i - 1] == -1:
        if i <= 2:
            arr[i - 1] = 2
        else:
            arr[i - 1] = (get_combination_count(i - 2) +
                          get_combination_count(i - 1))

    return arr[i - 1]

n = int(input())
arr = [-1] * n
print(get_combination_count(n))