#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, n1, i, j, k = 2;
  cin >> n;
  n1 = n - 2;
  if (n == 1)
    cout << "2" << endl;
  else if (n == 2)
    cout << "3" << endl;
  else {
    while (1) {
      if (n1 - k * 2 <= 0) break;
      n1 = n1 - k * 2;
      k++;
    }
    if (n1 <= k)
      cout << k * 2;
    else
      cout << k * 2 + 1;
  }
  return 0;
}
