#include <iostream>#include <vector>#include <algorithm>#include <cmath>#include <string.h>#include <stdio.h>using namespace std;#define MAX_N 100000 + 16typedef int type_xy;typedef struct Point{ int id; type_xy x, y; Point() {} Point(type_xy x, type_xy y) : x(x), y(y) {} Point operator + (Point p){ return Point(x + p.x, y + p.y); } Point operator - (const Point& p){ return Point(x - p.x, y - p.y); } Point operator * (type_xy d){ return Point(x*d, y*d); } bool operator < (const Point& a) const { if (x != a.x) return x < a.x; else return y < a.y; } type_xy dot(Point p) { return x*p.x + y*p.y; } type_xy det(Point p) { return x*p.y - y*p.x; }};Point P[MAX_N], Q[MAX_N];inline type_xy cross(Point A, Point B, Point C){ return (B - A).det(C - A);}inline type_xy compute_area(Point A, Point B, Point C){ type_xy res = cross(A, B, C); if (res < 0) { return -res; } return res;}inline type_xy compute_area(const vector<Point>& ps){ type_xy total = 0; for (int i = 2; i < ps.size(); ++i) { total += compute_area(ps[0], ps[i - 1], ps[i]); } return total;}vector <Point> convex_hull(Point *ps, int N){ sort(ps, ps + N); int k = 0; vector <Point> qs(N * 2); for (int i = 0; i < N; ++i) { while (k > 1 && (qs[k - 1] - qs[k - 2]).det(ps[i] - qs[k - 1]) <= 0) --k; qs[k++] = ps[i]; } for (int i = N - 2, t = k; i >= 0; --i) { while (k > t && (qs[k - 1] - qs[k - 2]).det(ps[i] - qs[k - 1]) <= 0) --k; qs[k++] = ps[i]; } qs.resize(k - 1); return qs;}int main(int argc, char *argv[]){ int N; while (~scanf("%d", &N) && N > 0) { for (int i = 0; i < N; ++i) { scanf("%d%d", &P[i].x, &P[i].y); P[i].id = i; } memcpy(Q, P, N * sizeof(Point)); vector<Point> ps = convex_hull(P, N); type_xy ans = 0x3f3f3f3f; for (int i = 0; i < ps.size(); ++i) { memcpy(P, Q, N * sizeof(Point)); swap(P[ps[i].id], P[N - 1]); ans = min(ans, compute_area(convex_hull(P, N - 1))); } printf("%d.%sn", ans / 2, ans % 2 == 1 ? "50" : "00"); } return 0;}
