import java.util.Arrays; public class Main { private static void solve() { int n = ni(); int[][] p = ntable(n, 2); double[] theta1 = new double[n]; double[] theta2 = new double[n]; for (int i = 0; i < n; i++) { theta1[i] = theta2[i] = Math.atan2(p[i][1], p[i][0]) + Math.PI; theta2[i] += Math.PI * 2; } Arrays.sort(theta1); Arrays.sort(theta2); long ret = 0; double eps = 0.000000000001; for (int i = 0; i < n; i++) { for (int j = i + 1; j < n; j++) { double s = theta1[i]; double t = theta1[j]; if (t - s + eps >= Math.PI) { break; } int x = lowerBound(theta2, Math.PI + s + eps, i); int y = lowerBound(theta2, Math.PI + t - eps, i); ret += Math.max(0, y - x); } } System.out.println(ret); } public static int lowerBound(double[] a, double v, int to) { int low = -1, high = to; while (high - low > 1) { int h = high + low >>> 1; if (a[h] >= v) { high = h; } else { low = h; } } return high; } public static void main(String[] args) { new Thread(null, new Runnable() { @Override public void run() { long start = System.currentTimeMillis(); String debug = args.length > 0 ? args[0] : null; if (debug != null) { try { is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug)); } catch (Exception e) { throw new RuntimeException(e); } } reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768); solve(); out.flush(); tr((System.currentTimeMillis() - start) + "ms"); } }, "", 64000000).start(); } private static java.io.InputStream is = System.in; private static java.io.PrintWriter out = new java.io.PrintWriter(System.out); private static java.util.StringTokenizer tokenizer = null; private static java.io.BufferedReader reader; public static String next() { while (tokenizer == null || !tokenizer.hasMoreTokens()) { try { tokenizer = new java.util.StringTokenizer(reader.readLine()); } catch (Exception e) { throw new RuntimeException(e); } } return tokenizer.nextToken(); } private static double nd() { return Double.parseDouble(next()); } private static long nl() { return Long.parseLong(next()); } private static int[] na(int n) { int[] a = new int[n]; for (int i = 0; i < n; i++) a[i] = ni(); return a; } private static char[] ns() { return next().toCharArray(); } private static long[] nal(int n) { long[] a = new long[n]; for (int i = 0; i < n; i++) a[i] = nl(); return a; } private static int[][] ntable(int n, int m) { int[][] table = new int[n][m]; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { table[i][j] = ni(); } } return table; } private static int[][] nlist(int n, int m) { int[][] table = new int[m][n]; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { table[j][i] = ni(); } } return table; } private static int ni() { return Integer.parseInt(next()); } private static void tr(Object... o) { if (is != System.in) System.out.println(java.util.Arrays.deepToString(o)); } }