int bsearch_1(int l,int r)
{
    int mid = r+l>>1;
    while(l<r)
    {
        if(check(mid)) r=mid;
        else l=mid+1;
    }
    return l;
}

int bsearch_2(int l,int r)
{
    int mid = r+l+1>>1;
    while(l<r)
    {
        if(check(mid)) l = mid;
        else r = mid-1;
    }
    return l;
}