#include <iostream>

using namespace std;

int main()
{
    int n,x,a,b,t;
    cin>>x;
    n=0;
    a=0;
    b=1;
    while(b<x)
        {t=a;
        a=b;
        b+=t;
        n++;
        }
   cout<<n;
return 0;
}