#include <algorithm>
#include <fstream>
#include <iostream>
#include <limits>

using namespace std;

long biggestBox(long H) { return 2 * H * H; }

long smallestBox(long H) { 
  long W = (H+1)/2;
  return H * W;
}

long rootXUpperBound(long x) { 
  long y = 1;
  while(y*y < x) {
    y *= 2;
  }
  return y;
}

long smallestHeightWithBigEnoughBox(long N) {
  long hHigh = 10 * rootXUpperBound(N);
  long hLow = 1;
  while (hHigh > hLow + 1) {
    long hMid = (hLow + hHigh) / 2;
    if (biggestBox(hMid) >= N) {
      hHigh = hMid;
    } else {
      hLow = hMid;
    }
  }

  if (biggestBox(hLow) >= N)
    return hLow;
  return hHigh;
}

long findBest(long N) {

  // Find the smallest height that allows us to make a box big enough to hold
  // the widgets
  long Hmin = smallestHeightWithBigEnoughBox(N);

  // Computing Hmax is subtle. Instead, search until the smallest box we can
  // make is already more wasteful than our best solution.
  long bestWasted = N + 1;
  for (long H = Hmin;; H++) {
    //cout << "Testing H = " << H << endl;

    // Stopping rule
    long smallestCap = smallestBox(H);
    if (smallestCap > N && smallestCap - N > bestWasted) {
      break;
    }

    // Test this height
    long bestW = (N+H-1)/H;
    long bestWCap = H*bestW;
    long cap = max(bestWCap, smallestCap);

    //cout << "  cap = " << cap << endl;
    bestWasted = min(bestWasted, cap - N);
  }
  
  return bestWasted;
}

void solve(istream &in) {
  long N;
  in >> N;

  long empty = findBest(N);

  cout << empty << endl;
}

int main(int argc, char **argv) {

  if (argc > 1) {
    ifstream in(argv[1]);
    if (!in) {
      cerr << "could not open stream" << endl;
      return -1;
    }
    solve(in);
  } else
    solve(cin);
}