#include <fstream>
#include <iostream>
using namespace std;
long long x,y,z,t;
int main()
{
    int i=0;
    cin>>x;
    z=0;y=1;
    while (y<=x) {
        t=y+z;
        z=y;
        y=t;
        i++;
    }
    cout<<i<<'\n';

    return 0;
}