int Min_rec (char **list, int x, int size, int nsam)
{  /* Calculate min # rec. events */
  int a, b, c, e, gtest, flag = 0;
  
  if (size<2 || x >= (size-1))
    return (0);
  for (a=x+1; a<size; ++a) {
    for (b=x; b<a; ++b) {
      gtest = 0;
      for (e=0; e<nsam; ++e)
        if (list[e][b] == '0' && list[e][a] == '0') {
          ++gtest;
          break;
        }
      for (e=0; e<nsam; ++e)
        if (list[e][b] == '0' && list[e][a] == '1') {
          ++gtest;
          break;
        }
      for (e=0; e<nsam; ++e)
        if (list[e][b] == '1' && list[e][a] == '0') {
          ++gtest;
          break;
        }
      for (e=0; e<nsam; ++e)
        if (list[e][b] == '1' && list[e][a] == '1') {
          ++gtest;
          break;
        }
      if (gtest == 4) {
        flag = 1;
        break;
      }
    }
    if (flag == 1)
      break;
  }
  if (a==size)
    return (0);
  else {
    c = Min_rec (list, a, size, nsam);
    return (1+c);
  }
}