x = int(input())
if x in range(1, 31):
    array = [1 for x in range(x)]
    for i in range(2, x):
        array[i] = array[i - 1] + array[i - 2]
    print(array[x - 1])
else:
    print("So %d khong nam trong khoang [1,30]." % x)