#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf(" %d", &n);
  int x = 1;
  int order = 0;
  int cnt = 0;
  for (int i = 2;; i++, order++) {
    if (order % 2 == 0) cnt++;
    x += cnt;
    if (n <= x - 1) {
      printf("%d\n", i);
      return 0;
    }
  }
}
