#include <bits/stdc++.h>
using namespace std;
const int inf = 0x20202020;
const long long mod = 1000000007;
const double eps = 1e-9;
const double pi = 3.1415926535897932384626;
const int DX[] = {1, 0, -1, 0}, DY[] = {0, 1, 0, -1};
long long powmod(long long a, long long b) {
  long long res = 1;
  a %= mod;
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % mod;
    a = a * a % mod;
  }
  return res;
}
long long powmod(long long a, long long b, long long mod) {
  long long res = 1;
  a %= mod;
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % mod;
    a = a * a % mod;
  }
  return res;
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
int n;
long long x, y;
int main() {
  scanf("%d", &n);
  if (n == 0) return puts("1"), 0;
  x = n / sqrt(2);
  y = sqrt(1ll * n * n - x * x);
  printf("%I64d\n", 4 * (x + y));
}
