unsigned long binsearch(unsigned long long int nel, int (*less)(unsigned long i,unsigned long j))
{
    unsigned long long int low = 0, high = nel-1, mid;
    while ( low <= high)
    {
        mid = low/2+high/2;
        if (less(high-1,high)&&less(high+1,high))
            return high;
        if (less(low-1,low)&&less(low+1,low))
            return low;
        if (less(mid-1,mid) && less(mid+1,mid))
            return mid;
        if(less(mid-1,mid))
            low = mid + 1;
        else
            if (less(mid+1,mid))
                high = mid - 1;
            else
                low=mid +1;
    }
    return nel;
}

unsigned long peak(unsigned long nel,
        int (*less)(unsigned long i, unsigned long j))
{
   return binsearch(nel,less);
}