#include <bits/stdc++.h>
using namespace std;
long long int mod = 1000000007;
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  long long int n;
  cin >> n;
  if (n == 1) {
    cout << 2;
    return 0;
  }
  if (n == 2) {
    cout << 3;
    return 0;
  }
  long long int curr = 2, line = 3, to = 2;
  while (to < n) {
    line++;
    to += curr;
    if (to >= n) {
      cout << line;
      return 0;
    }
    line++;
    to += (curr);
    curr++;
    if (to >= n) {
      cout << line;
      return 0;
    }
  }
}
