#include <iostream>
using namespace std;

int main()
{
    unsigned long long n,p,a,b,c;
    cin>>n;
    if(n==0)
        cout<<0;
    else
        if(n==1)
            cout<<1;
        else
        {
            a=0;b=1;p=1;
            while(b<n)
            {
                c=b+a;
                a=b;b=c;
                p++;
            }
            cout<<p-1;

        }
    return 0;
}