#include <bits/stdc++.h>
using namespace std;
long long n, l, r, tg;
long long tinh(long long x) {
  if (x % 2 == 0)
    return (x / 2) * (x / 2);
  else
    return (x / 2) * (x / 2 + 1);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cin >> n;
  l = 2;
  r = 100000;
  tg = (l + r) / 2;
  while (l != r) {
    if (tinh(tg) >= n)
      r = tg;
    else
      l = tg + 1;
    tg = (r + l) / 2;
  }
  cout << tg;
  return 0;
}
