20211022.py

def cyc(a, b, lim):
	c = a + b
	if c > lim:
		return b
	return  cyc(b, c, lim)

limin = input()
lim = 0
try:
	lim = int(limin)
except ValueError as e:
	print('整数を入力してください')
	exit()

x = cyc(1, 1, lim)
print(x)