int lst = -1;
unsigned lstx;
int binary_search(const unsigned *a, int n, unsigned x)
{
register int l, r;
if (lst > 0)
if (x > lstx) l = lst + 1, r = n - 1;
else r = lst - 1, l = 0;
else l = 0, r = n - 1;
lstx = x;
while (l <= r)
{
int mid = l + r >> 1;
if (a[mid] == x) return lst = mid;
else if (a[mid] < x) l = mid + 1;
else r = mid - 1;
}
}