#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  long long l = 0, r = n + 1;
  long long t = 1e9;
  while (l != r) {
    long long mid = (l + r) / 2;
    long long a = mid / 2;
    long long b = mid - a;
    if (a * b >= n) {
      r = mid;
    } else {
      l = mid + 1;
    }
  }
  cout << l << endl;
  return 0;
}
