#include <iostream>

using namespace std;

int main()
{
    int n,x,a0,a1,a2;
    cin>>x;

    if(x==1)
        cout<<0;
    n=0;
    a2=0;
    a0=0;
    a1=1;
    while(a2<x)
        {
        n++;
        a2=a1+a0;
        a0=a1;
        a1=a2;
        }
   cout<<n;
return 0;
}