package adv2019; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.Comparator; import java.util.InputMismatchException; public class D10_5 { InputStream is; PrintWriter out; String INPUT = ""; void solve() { int n = ni(); int[][] co = new int[n][]; for(int i = 0;i < n;i++) { co[i] = na(2); } out.println(countTrianglesContainingOX(co)); } public static long countTrianglesContainingO(int[][] co) { int n = co.length; Arrays.sort(co, compArgi); long ret = (long)n*(n-1)*(n-2)/6; for(int h = 0, t = 0, hm = 0, tm = 0;h < 2*n;h++, hm++) { if(hm == n)hm = 0; while(t < h && cross(co[hm], co[tm]) > 0) { if(++tm == n)tm = 0; t++; } if(h >= n)ret -= (long)(h-t)*(h-t-1)/2; } return ret; } public static long countTrianglesContainingOX(int[][] co) { int n = co.length; Arrays.sort(co, compArgi); long ret = (long)n*(n-1)*(n-2)/6; long sameline = 0; for(int h = 0, t = 0, t2 = 0, hm = 0, tm = 0, t2m = 0;h < 2*n;h++, hm++) { if(hm == n)hm = 0; while(t < h && (cross(co[hm], co[tm]) > 0 || cross(co[hm], co[tm]) == 0 && dot(co[hm], co[tm]) > 0)) { if(++tm == n)tm = 0; t++; } while(t2 < h && (cross(co[hm], co[t2m]) > 0 || cross(co[hm], co[t2m]) == 0 && dot(co[hm], co[t2m]) < 0)) { if(++t2m == n)t2m = 0; t2++; } if(h >= n) { ret -= (long)(h-t)*(h-t-1)/2 - (t2-t)*(t2-t-1)/2; } } return ret + sameline; } public static long dot(int[] a, int[] b){ return (long)a[0]*b[0]+(long)a[1]*b[1]; } public static long cross(int[] a, int[] b){ return (long)a[0]*b[1]-(long)a[1]*b[0]; } public static Comparator compArgi = new Comparator(){ public int compare(int[] a, int[] b) { long ax = a[0], ay = a[1]; long bx = b[0], by = b[1]; int za = ay > 0 || ay == 0 && ax > 0 ? 0 : 1; int zb = by > 0 || by == 0 && bx > 0 ? 0 : 1; if(za != zb)return za - zb; if(ay*bx-ax*by != 0)return Long.signum(ay*bx-ax*by); return Long.signum((ax*ax+ay*ay)-(bx*bx+by*by)); } }; void run() throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){ // @Override // public void run() { // long s = System.currentTimeMillis(); // solve(); // out.flush(); // if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // } // }; // t.start(); // t.join(); } public static void main(String[] args) throws Exception { new D10_5().run(); } private byte[] inbuf = new byte[1024]; public int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ') sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private long[] nal(int n) { long[] a = new long[n]; for(int i = 0;i < n;i++)a[i] = nl(); return a; } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[][] nmi(int n, int m) { int[][] map = new int[n][]; for(int i = 0;i < n;i++)map[i] = na(m); return map; } private int ni() { return (int)nl(); } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }