# your code goes here
n=int(input())
def fibo(n):
if n == 0:
return 0
elif n==1 or n==2:
return 1
else:
return fibo(n-1) + fibo(n-2)
print(fibo(n))
IyB5b3VyIGNvZGUgZ29lcyBoZXJlCm49aW50KGlucHV0KCkpCgpkZWYgZmlibyhuKToKCWlmIG4gPT0gMDoKCQlyZXR1cm4gMAoJZWxpZiBuPT0xIG9yIG49PTI6CgkJcmV0dXJuIDEKCWVsc2U6CgkJcmV0dXJuIGZpYm8obi0xKSArIGZpYm8obi0yKQoKcHJpbnQoZmlibyhuKSk=