#include <iostream>
#include <cmath>
using namespace std;

int main() {
    unsigned long long x ;
    cin >> x;
    unsigned long long a = 1, b = 1, nr = 0, c = a + b;
    while(c < x)
    {
        c = a + b;
        a = b;
        b = c;
        nr ++;
    }
    cout << nr + 1;
    return 0;
}