#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 5e4 + 10;
void solve()
{
	int n; cin >> n;
	if(n == 1) 
	{
		cout << 1 << "\n";
		return;
	}
	vector<int> a(N + 1);
	a[0] =  1;
	for(int i = 3; i < N; i++)
	{
		for(int j = i / 2; j > 0; j--)
		{
			if(j == i / 2 && i & 1)
			{
				a[j] = a[j - 1] * 2;
			}
			else a[j] += a[j - 1];
			
			if(a[j] == n)
			{
				cout << i * (i - 1) / 2 + j + 1 << "\n";
				return;
			}
		}
	}
	
	cout << n * (n + 1) / 2 + 2 << "\n";
}
signed main()
{
	
	ios::sync_with_stdio(false);
	cin.tie(0);
	int t = 1; 
	while(t--) solve();
	return 0;
}