#include <iostream>
#include <cmath>

using namespace std;

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