模板：

int l,r;
while(l<r)
{
    int mid=l+r>>1;
    if(q[mid]>=x)r=mid;
    else l=mid+1;
}



int l,r;
while(l<r)
{
    int mid=l+r+1>>1;
    if(q[mid]<=x)l=mid;
    else r=mid-1;
}


double l,r;
    while(abs(r-l)>eps)
    {
        double mid=(l+r)/2;
        if(mid*mid*mid>=n)r=mid;
        else l=mid;
    }