void convex_hull(poly & t, poly & r) {
unsigned i;
Compare order;
// Search leftmost vertex
order.p0 = t[0];
for (i = 1; i < t.size(); ++i)
if (t[i].real() < order.p0.real())
order.p0 = t[i];
sort(t.begin(), t.end(), order);
for (i = 0; i < t.size(); ++i) {
r.push_back(t[i]);
// Pop vertices that become internal
while (r.size() > 3u && angle(r.end()[-3], r.end()[-2], r.end()[-1])) {
r.end()[-2] = r.back();
r.pop_back();
}
}
return;
}
inline void reduce(poly &a){
int N = (int)a.size();
while (N > 0 && a[N - 1] == 0)a.pop_back(), N--;
}
