#include <iostream>

using namespace std;


int main()
{
    int t1=0;
    int anterior=0, aux=0;
    int t2=1;
    int x;
    cin>>x;
    while (aux<x){
        anterior+=1;
        aux=t1+t2;
        t1=t2;
        t2=aux;

    }
    cout<<anterior;
    return 0;
}