void merge(int vet[], int ini, int mid, int fim) {
  static int left[MAX_N+1], right[MAX_N+1];
  memcpy(left , &vet[  ini], sizeof(int)*(mid-ini+1));
  memcpy(right, &vet[mid+1], sizeof(int)*(  fim-mid));
  left [mid-ini+1] = MAX_INT;
  right[  fim-mid] = MAX_INT;
  for (int i = ini, j = 0, k = 0; i <= fim; i++) {
    vet[i] = (left[j] <= right[k] ? left[j++] : right[k++]);
  }
}