int BSearch(int[] x, int n, int t) {
    int l = -1, u = n, p = 0, m = 0;
 
    while (l + 1 != u) {
        m = (l + u) /2;
 
        if (x[m] <  t) {
            l = m;
        } else {
            u = m;
        }
    }
 
    p = u;
    if (p >= n || x[p] != t) {
        p = -1;
    }
    return p;
}