#include <bits/stdc++.h>
using namespace std;
long long n, a, c, b, skrng;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  a = 1;
  b = 1;
  skrng = 0;
  while (a + b <= n) {
    c = a;
    a = b;
    b = c + b;
    skrng++;
  }
  cout << skrng << '\n';
  return 0;
}
