#include <iostream>

using namespace std;

int main()
{
    long long r;
    cin >> r;
    long long x = r;
    long long num = r;
    for (int i = 1; i < r; ++i) {
        while (x * x + i * i > r * r)
            --x;
        num += x;
    }
    cout << num * 4 + 1;
    return 0;
}