#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n = 0, x = 0;
  cin >> n >> x;
  long long result = 0;
  if (n % 2 != 0)
    result = 3 * (n - 1);
  else {
    if (x < n / 2)
      result = 3 * (n - x);
    else
      result = 3 * x;
  }
  printf("%li\n", result);
}
