#include <bits/stdc++.h>
using namespace std;
long long n;
bool si = true;
long long res = 0, pos = 0, mov = 0, t = 1, con = 1, ss = 1;
int main() {
  cin >> n;
  while (si) {
    pos += con;
    t++;
    mov++;
    if (mov == 2) {
      mov = 0;
      con++;
    }
    if (n <= pos) {
      cout << t;
      break;
    }
  }
}
