题解 | #统计每个月兔子的总数#

month = int(input())
rabnum = {'能生':1,'不能生':[[3,1]]}
if month <= 3:  
    print("2") 
else:
    for i in range(4,month+1):
        for j in rabnum['不能生']:
            if i-j[0]+1 == 3:
                rabnum['能生'] += j[1]
                rabnum['不能生'].remove(j)
        rabnum['不能生'].append([i,rabnum['能生']])
    resault = 0
    for i in rabnum['不能生']:
        resault +=i[1]
    print(resault+rabnum['能生'])