pair<double, double> a(4.0, 5.0);
pair<double, double> a(5.0, 4.0);

bool equal ( /* pair p1 and p2 */)
{ /*check if p1 first and p2 first are equal
      if so, check if p1 second and p2 second are equal
        if so, return true
    if 1st check not, check if p1 first and p2 second are equal
      if so, check if p1 second and p2 first are equal
        if so, return true
    return false otherwise */
}