#include <bits/stdc++.h>
using namespace std;
int main ()
{
    long long x,a,b,nr=1,cnt=2;
    cin>>x;
    a=0;
    b=1;
    while(nr<x)
    {
        cnt++;
        nr=b+a;
        a=b;
        b=nr;
    }
    cnt-=2;
    cout<<cnt;
}