#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.tie(NULL);
  ios_base::sync_with_stdio(false);
  long long n;
  cin >> n;
  if (n == 1) {
    cout << 2 << endl;
    return 0;
  }
  if (n == 2) {
    cout << 3 << endl;
    return 0;
  }
  long long a[100002];
  long long k = 0;
  for (long long i = 0; i < 100001; i += 2) {
    a[i] = k + 2;
    a[i + 1] = k + 2;
    k++;
  }
  long long z = 2, m;
  for (m = 0; m < 100001; m++) {
    z += a[m];
    if (z > n) break;
  }
  if (z - a[m] < n)
    cout << m + 4 << endl;
  else
    cout << m - 1 + 4 << endl;
}
