def fib(a):
tab = [0, 1]
for i in range(a-1):
tab.append(tab[i] + tab[i+1])
print(fib(int(input())))
ZGVmIGZpYihhKToKICAgdGFiID0gWzAsIDFdCiAgIGZvciBpIGluIHJhbmdlKGEtMSk6CiAgICAgICB0YWIuYXBwZW5kKHRhYltpXSArIHRhYltpKzFdKQpwcmludChmaWIoaW50KGlucHV0KCkpKSk=