Is UUID version 5 or not?

isuuid5.cc

#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>

using namespace std;

int main() {
  cout << "Enter uuid: ";
  string input;
  cin >> input;

  input.erase(std::remove(input.begin(), input.end(), '-'), input.end());
  string important_bits = input.substr(12,4);

  // Convert to string (hex) to long
  long int value;
  istringstream iss(important_bits);
  iss >> hex >> value;

  int version = value & 0xf;

  if (version == 5) {
    cout << "UUID is version 5.";
  }
  else {
    cout << "UUID is not version 5";
  }

  cout << endl;

  return 0;
}