Problem link: https://acm.timus.ru/problem.aspx?space=1&num=1522

In this problem all you have to do is to come up with clever sorting comparator.

This one is fine:

struct info_t {
  int a, b, c, id;
  int get() const {
    if (a <= c) {
      return (a + b);
    } else {
      return -(b + c);
    }
  }
  bool operator <(const info_t &y) const {
    int xg = this->get(), yg = y.get();
    if (sgn(xg) != sgn(yg)) {
      return sgn(xg) > sgn(yg);
    } else {
      return xg < yg;
    }
  }
};