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

using namespace std;

long lSqrt (long N)
{
	if (N <= 1)
		return N;
	long maxSqrt = 1;
	while (maxSqrt * maxSqrt <= N)
	{
		maxSqrt *= 2L;
	}
	long minSqrt = maxSqrt / 2L;
	while (minSqrt < maxSqrt)
	{
		long mid = (minSqrt + maxSqrt) / 2L;
		long sqr = mid*mid;
		if (sqr == N)
			return mid;
		else if (sqr < N)
		{
			minSqrt = mid + 1;
		}
		else
			maxSqrt = mid;
	}
	return minSqrt-1L;
}


long pack(long N)
{
	long bestSoFar = numeric_limits<long>::max();
	long stop = lSqrt(N)+1;
	long start = max(1L, 7 * (stop-1L) / 10); // slightly less than sqrt(2.0) * stop
	for (long h = start; h <= stop; ++h)
	{
			long w = N / h;
			if (2*h >= w)
			{
				if (h*w == N)
				{
					bestSoFar = 0;
					//cerr << N << " can be factored as " << h << " by " << w << endl;
					break;
				}
				else
				{
					++w;
					if (2*h >= w)
					{
						long boxSize = h*w;
						bestSoFar = min(bestSoFar, boxSize - N);
						/*
						cerr << "Looked at " << h << " by " << w << " = "
								<< boxSize << endl;
						cerr << "best so far: " << bestSoFar << endl;
						*/
					}
				}
		}
	}

	return bestSoFar;
}


void solve (istream& in)
{
	//cerr << "Accepting input up to " << numeric_limits<long>::max() << endl;
	long N;
	in >> N;

	long empty = pack(N);

	cout << empty << endl;
}




int main (int argc, char** argv)
{
	if (argc > 1)
	{
		ifstream in (argv[1]);
		solve (in);
	}
	else
		solve (cin);
}