unsigned long peak(unsigned long nel, int(*less)(unsigned long i, unsigned long j))
{
    if (nel < 3) return less(0, 1);
    for (unsigned long k = 1; k < (nel - 1); k++) {
        if(less(k-1, k) && less(k+1, k)) return k;
    }
}

int less(unsigned long i, unsigned long j)
{
    if (i == j) return 0;

    if (i < j) {
        if (j <= 11241155978086311589UL) return 1;
        if (i >= 11241155978086311589UL) return 0;
        return (11241155978086311589UL-i) < (j-11241155978086311589UL);
    }

    if (i <= 11241155978086311589UL) return 0;
    if (j >= 11241155978086311589UL) return 1;
    return (11241155978086311589UL-j) < (i-11241155978086311589UL);
}

unsigned long peak(unsigned long, int (*)(unsigned long, unsigned long));

int main(int argc, char **argv)
{
    unsigned long i = peak(13356955260197607378UL, less);
    if (i == 11241155978086311589UL) {
        printf("CORRECTn");
    } else {
        printf("WRONGn");
    }
    return 0;
}