#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  vector<long long> dp;
  dp.push_back(0);
  dp.push_back(1);
  while (dp.back() <= n - 1) {
    dp.push_back(dp[dp.size() - 1] + dp[dp.size() - 2] + 1);
  }
  cout << dp.size() - 2 << endl;
}
