void merge_sort(int *num, int low, int hig, int *t)
{
    int mid = low+(hig-low)/2;
    if (hig-low>1)
    {
        int e = low, p = mid, i = low;
        merge_sort(num, low, mid, t);
        merge_sort(num, mid, hig, t);
        while ((e<mid) || (p<hig))
        {
            if ((P>=hig) || (e<mid && num[e]<num[p])) t[i++] = num[e++];
            else t[i++] = num[p++];
        }
        for (i=low; i<hig; i++) num[i] = t[i];
    }
}