Огненный круг

#define _USE_MATH_DEFINES
#include <iostream>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <vector>
#include <stdio.h>
#include <cmath>
#include <math.h>
#include <queue>
#include <stack>
#include <climits>
#include <deque>
#include <ctime>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;

#define mh() make_heap()
#define poph() pop_heap()
#define pushh() push_heap()
#define sor(n) n.begin(), n.end()

int main()
{
    ll r;
    cin >> r;
    ll sc = 0;
    for (ll x = 0; x < r; x++)
    {
        sc += ceil(sqrt((double)r*r - x*x));
    }
    cout << sc * 4;
    system("pause");
    return 0;
}