#include <bits/stdc++.h>
#define ever ( ; ; )
using namespace std ;

int main () {

    int64_t x = 1 , y , z , a , b , p = ( 1LL << 62 ) + 5 , n , cnt = 2 ;
    cin >> n ;
    z = 0 , y = 1 ;
    if ( n == 1 )   return cout << 0 , 0 ;
    if ( n == 2 )   return cout << 2 , 0 ;
    for ever    {
        a = x ;
        b = y ;
        x = a + b ;
        y = a ;
        z = b ;
        if ( x >= n )   return cout << cnt , 0 ;
        cnt ++ ;
    }
}