python递归题解

def f(n):
s = 0
a,b = 1,2
_ = 2
if n == 1 or n == 2:
s = n
print(s)
else:
while True:
if _ == n:
print(s)
break
else:
s = a + b
a = b
b = s
_ += 1
n = int(input())
f(n)