try:
    n = int(input('Enter N: '))

    a, b, c = 0, 1, 1

    counter = 2
    while c < n:
        a, b, c = b, c, b + c
        counter += 1

    if c == n:
        print (counter)
    elif (c - n == n - b):
        print (c)
    else:
        if (c - n > n - b):
            print (b)
        else:
            print (c)
except ValueError:
    print("That's incorrect N")