#include <iostream>
using namespace std;
long long a,b,x,fib,p;
int main()
{
    cin>>x;
    if(x==1) {cout<<0; return 0;}
    if(x==2) {cout<<1; return 0;}
    if(x==3) {cout<<2; return 0;}

    a=0;
    b=1;
    fib=1;
    p=2;
    while(fib<x)
    {
        a=b;
        b=fib;
        if(a+b>=x) break;
        fib=a+b;
        p++;

    }

    cout<<p;
    return 0;
}