653 B | 653 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from decimal import Decimal
BLANK = " "
inp = input
# inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
n = ii()
l = [1, 1]
for i in range(17):
l.append(l[-1] + l[-2])
s = [1, 2]
for i in range(2, len(l)):
s.append(s[-1] + l[i])
for i in range(len(s)):
if s[i] >= n:
p(i + 1)
break
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()