#include <iostream>
#include <fstream>
#include <map>
#include <string>
using namespace std;
ifstream fin("fib.in");
ofstream fout("fib.out");
unsigned long long x, fib[1000], ind[1000], i, rez;

int main()
{
    cin >> x;
    fib[0] = ind[0] = 0;
    fib[1] = ind[1] = 1;

    i = 2;
    while(i <= 93)
    {


        fib[i] = fib[i - 1] + fib[i - 2];
        ind[i] = i;
        i++;
    }
    for(int j=0;j<i;j++)
        if(fib[j] < x)
            rez = ind[j];

    cout << rez;
    return 0;
}