#include <bits/stdc++.h>
using namespace std;

#define rep(i, n) for (int i = 0; i < (int)n; i++)
using ll = long long int;

int main() {
  ll n;
  cin >> n;
  ll i = 0;
  int ans = 0;
  ll p = 2;
  while (i < n) {
    ans++;
    i += p + 1;
    p += 2;
  }
  cout << ans << endl;
  return 0;
}