static void doubleReTok(L<S> tok, int i1, int j1, int i2, int j2) {
  if (i1 > i2) {
    int i = i1, j = j1;
    i1 = i2; j1 = j2;
    i2 = i; j2 = j;
  }
  if (j1 > i2) { reTok(tok); ret; }
  reTok(tok, i2, j2);
  reTok(tok, i1, j1);
}