题解 | #统计每个月兔子的总数#

'''斐波那契数列
1    1          
1    1
2    1                                                    1
3    1                  1                                 1
5    1       1          1                                 1       1
8    1 1     1          1  1                              1 1     1
13   1 1 1   1 1        1 1 1                             1 1 1   1 1
'''

n=int(input())
start=0
total=1
if n==1:
    print(total)
elif n>1:
    for i in range(2,n+1):
        start,total=total,start+total
print(total)