735C - Tennis Championship - CodeForces Solution

import os
import sys
from io import BytesIO, IOBase
from collections import defaultdict


def fastfib(n):
    
    bin_of_n = bin(n)[2:]      f = [0, 1]  
    for b in bin_of_n:
        f2i1 = f[1]**2 + f[0]**2          f2i = f[0]*(2*f[1]-f[0])  
        if b == '0':
            f[0], f[1] = f2i, f2i1          else:
            f[0], f[1] = f2i1, f2i1+f2i  
    return f[0]


def main():
    n = int(input())

    l, r = 0, 100

    while r - l > 1:
        mid = (l + r) // 2
        if fastfib(mid) > n:
            r = mid
        else:
            l = mid

    print(l-2)




BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._file = file
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")


if __name__ == "__main__":
    main()