You are given n points on a plane. All the points are distinct and no three of them lie on the same line. Find the number of parallelograms with the vertices at the given points.

Input

The first line of the input contains integer n (1 ≤ n ≤ 2000) — the number of points.

Each of the next n lines contains two integers (xi, yi) (0 ≤ xi, yi ≤ 109) — the coordinates of the i-th point.

Output

Print the only integer c — the number of parallelograms with the vertices at the given points.

Example

Input

4
0 1
1 0
1 1
2 0


Output

1
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Writer;
import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.StringTokenizer;

public class CodeD {
  private static final boolean SHOULD_BUFFER_OUTPUT = false;

  static final SuperWriter sw = new SuperWriter(System.out);

  static final SuperScanner sc = new SuperScanner();


  static class Rational implements Comparable <Rational> 
  {
      static Rational zero = new Rational(0, 1);
      
      private long num;
      private long den;

      public Rational(long numerator, long denominator) {
          long g = gcd(numerator, denominator);
          num = numerator   / g;
          den = denominator / g;
          if (den < 0) { den = -den; num = -num; }
      }

      public long numerator()   { return num; }
      public long denominator() { return den; }

      public String toString() { 
          if (den == 1) return num + "";
          else          return num + "/" + den;
      }

      public int compareTo(Rational b) {
          Rational a = this;
          long lhs = a.num * b.den;
          long rhs = a.den * b.num;
          if (lhs < rhs) return -1;
          if (lhs > rhs) return +1;
          return 0;
      }

      public boolean equals(Object y) {
          Rational b = (Rational) y;
          return compareTo(b) == 0;
      }

      public int hashCode() {
          return this.toString().hashCode();
      }

      private long gcd(long m, long n) {
          if (m < 0) m = -m;
          if (n < 0) n = -n;
          if (0 == n) return m;
          else return gcd(n, m % n);
      }

      public long lcm(long m, long n) {
          if (m < 0) m = -m;
          if (n < 0) n = -n;
          return m * (n / gcd(m, n)); 
      }

      public Rational times(Rational b) {
          Rational a = this;
          Rational c = new Rational(a.num, b.den);
          Rational d = new Rational(b.num, a.den);
          return new Rational(c.num * d.num, c.den * d.den);
      }
      
      public Rational plus(Rational b) {
          Rational a = this;
          if (a.compareTo(zero) == 0) return b;
          if (b.compareTo(zero) == 0) return a;
          long f = gcd(a.num, b.num);
          long g = gcd(a.den, b.den);
          
          Rational s = 
          new Rational((a.num / f) * (b.den / g) + (b.num / f) * (a.den / g),
          lcm(a.den, b.den));
          
          s.num *= f;
          return s;
      }

      public Rational negate() {
          return new Rational(-num, den);
      }

      public Rational minus(Rational b) {
          Rational a = this;
          return a.plus(b.negate());
      }

      public Rational reciprocal() { return new Rational(den, num);  }

      public Rational divides(Rational b) {
          Rational a = this;
          return a.times(b.reciprocal());
      }
      
      public Rational abs() {
          if(num < 0)
              return negate();
          else
              return this;
      }
  }

  static class Line {
    Rational slope;
    long lengthSquare;
    boolean infiniteX;
    Integer hash;

    Line(long x1, long y1, long x2, long y2) {
      lengthSquare = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
      if (x1 == x2) {
        infiniteX = true;
        slope = new Rational(0, 1);
      } else {
        infiniteX = false;
        slope = new Rational(y2 - y1, x2 - x1);
      }
    }

    @Override
    public int hashCode() {
      if (hash != null) {
        return hash;
      }
      final int prime = 31;
      int result = 1;
      result = prime * result + (infiniteX ? 1231 : 1237);
      result = prime * result + (int) (lengthSquare ^ (lengthSquare >>> 32));
      result = prime * result + slope.hashCode();
      return hash = result;
    }

    @Override
    public boolean equals(Object obj) {
      Line other = (Line) obj;
      if (lengthSquare != other.lengthSquare) return false;
      if (infiniteX != other.infiniteX) return false;
      return slope.equals(other.slope);
    }
  }

  public static void main() {
    int n = sc.nextInt();
    int[][] points = sc.nextIntMatrix(n, 2);
    HashMap<Line, Long> lines = new HashMap<Line, Long>();
    for (int i = 0; i < n; i++) {
      for (int j = i + 1; j < n; j++) {
        long x1 = points[i][0];
        long y1 = points[i][1];
        long x2 = points[j][0];
        long y2 = points[j][1];

        Line line = new Line(x1, y1, x2, y2);
        if (!lines.containsKey(line)) {
          lines.put(line, 0L);
        }
        lines.put(line, lines.get(line) + 1L);
      }
    }
    long answer = 0;
    for (long value : lines.values()) {
      answer += value * (value - 1L);
    }
    sw.printLine(answer / 4L);
  }

  static class LineScanner extends Scanner {
    private StringTokenizer st;

    public LineScanner(String input) {
      st = new StringTokenizer(input);
    }

    @Override
    public String next() {
      return st.hasMoreTokens() ? st.nextToken() : null;
    }

    @Override
    public String nextLine() {
      throw new RuntimeException("not supported");
    }

    public boolean hasNext() {
      return st.hasMoreTokens();
    }

    private final ArrayList<Object> temp = new ArrayList<Object>();

    private void fillTemp() {
      while (st.hasMoreTokens()) {
        temp.add(st.nextToken());
      }
    }

    public String[] asStringArray() {
      fillTemp();
      String[] answer = new String[temp.size()];
      for (int i = 0; i < answer.length; i++) {
        answer[i] = (String) temp.get(i);
      }
      temp.clear();
      return answer;
    }

    public int[] asIntArray() {
      fillTemp();
      int[] answer = new int[temp.size()];
      for (int i = 0; i < answer.length; i++) {
        answer[i] = Integer.parseInt((String) temp.get(i));
      }
      temp.clear();
      return answer;
    }

    public long[] asLongArray() {
      fillTemp();
      long[] answer = new long[temp.size()];
      for (int i = 0; i < answer.length; i++) {
        answer[i] = Long.parseLong((String) temp.get(i));
      }
      temp.clear();
      return answer;
    }

    public double[] asDoubleArray() {
      fillTemp();
      double[] answer = new double[temp.size()];
      for (int i = 0; i < answer.length; i++) {
        answer[i] = Double.parseDouble((String) temp.get(i));
      }
      temp.clear();
      return answer;
    }
  }

  static class SuperScanner extends Scanner {
    private InputStream stream;
    private byte[] buf = new byte[8096];
    private int curChar;
    private int numChars;

    public SuperScanner() {
        this.stream = System.in;
    }

    public int read() {
        if (numChars == -1)
            return -1;
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = stream.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0)
                return -1;
        }
        return buf[curChar++];
    }
    
    public static boolean isWhitespace(int c) {
      return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }

    public static boolean isLineEnd(int c) {
      return c == '\n' || c == -1;
    }
    
    private final StringBuilder sb = new StringBuilder();
    
    @Override
    public String next() {
      int c = read();
      while (isWhitespace(c)) {
          if (c == -1) {
            return null;
          }
          c = read();
      }
      sb.setLength(0);
      do {
          sb.append((char) c);
          c = read();
      } while (!isWhitespace(c));
      return sb.toString();
    }

    @Override
    public String nextLine() {
      sb.setLength(0);
      int c;
      while (true) {
        c = read();
        if (!isLineEnd(c)) {
          sb.append((char) c);
        } else {
          break;
        }
      }
      if (c == -1 && sb.length() == 0) {
        return null;
      } else {
        if (sb.length() > 0 && sb.charAt(sb.length() - 1) == '\r') {
          return sb.substring(0, sb.length() - 1);
        } else {
          return sb.toString();
        }
      }
    }

    public LineScanner nextLineScanner() {
      String line = nextLine();
      if (line == null) {
        return null;
      } else {
        return new LineScanner(line);
      }
    }

    public LineScanner nextNonEmptyLineScanner() {
      while (true) {
        String line = nextLine();
        if (line == null) {
          return null;
        } else if (!line.isEmpty()) {
          return new LineScanner(line);
        }
      }
    }

    @Override
    public int nextInt() {
        int c = read();
        while (isWhitespace(c)) {
            c = read();
        }
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9')
                throw new InputMismatchException();
            res = (res << 3) + (res << 1);
            res += c - '0';
            c = read();
        } while (!isWhitespace(c));
        return res * sgn;
    }

    @Override
    public long nextLong() {
        int c = read();
        while (isWhitespace(c))
            c = read();
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        long res = 0;
        do {
            if (c < '0' || c > '9')
                throw new InputMismatchException();
            res = (res << 3) + (res << 1);
            res += c - '0';
            c = read();
        } while (!isWhitespace(c));
        return res * sgn;
    }
  }
  
  static abstract class Scanner {

    public abstract String next();

    public abstract String nextLine();

    public int nextIntOrQuit() {
      Integer n = nextInteger();
      if (n == null) {
        sw.close();
        System.exit(0);
      }
      return n.intValue();
    }

    public int nextInt() {
      return Integer.parseInt(next());
    }

    public long nextLong() {
      return Long.parseLong(next());
    }

    public double nextDouble() {
      return Double.parseDouble(next());
    }

    public int[] nextIntArray(int n) {
      int[] res = new int[n];
      for (int i = 0; i < res.length; i++)
        res[i] = nextInt();
      return res;
    }

    public long[] nextLongArray(int n) {
      long[] res = new long[n];
      for (int i = 0; i < res.length; i++)
        res[i] = nextLong();
      return res;
    }

    public double[] nextDoubleArray(int n) {
      double[] res = new double[n];
      for (int i = 0; i < res.length; i++)
        res[i] = nextDouble();
      return res;
    }

    public void sortIntArray(int[] array) {
      Integer[] vals = new Integer[array.length];
      for (int i = 0; i < array.length; i++)
        vals[i] = array[i];
      Arrays.sort(vals);
      for (int i = 0; i < array.length; i++)
        array[i] = vals[i];
    }

    public void sortLongArray(long[] array) {
      Long[] vals = new Long[array.length];
      for (int i = 0; i < array.length; i++)
        vals[i] = array[i];
      Arrays.sort(vals);
      for (int i = 0; i < array.length; i++)
        array[i] = vals[i];
    }

    public void sortDoubleArray(double[] array) {
      Double[] vals = new Double[array.length];
      for (int i = 0; i < array.length; i++)
        vals[i] = array[i];
      Arrays.sort(vals);
      for (int i = 0; i < array.length; i++)
        array[i] = vals[i];
    }

    public String[] nextStringArray(int n) {
      String[] vals = new String[n];
      for (int i = 0; i < n; i++)
        vals[i] = next();
      return vals;
    }

    public Integer nextInteger() {
      String s = next();
      if (s == null)
        return null;
      return Integer.parseInt(s);
    }

    public int[][] nextIntMatrix(int n, int m) {
      int[][] ans = new int[n][];
      for (int i = 0; i < n; i++)
        ans[i] = nextIntArray(m);
      return ans;
    }

    public char[][] nextGrid(int r) {
      char[][] grid = new char[r][];
      for (int i = 0; i < r; i++)
        grid[i] = next().toCharArray();
      return grid;
    }

    public static <T> T fill(T arreglo, int val) {
      if (arreglo instanceof Object[]) {
        Object[] a = (Object[]) arreglo;
        for (Object x : a)
          fill(x, val);
      } else if (arreglo instanceof int[])
        Arrays.fill((int[]) arreglo, val);
      else if (arreglo instanceof double[])
        Arrays.fill((double[]) arreglo, val);
      else if (arreglo instanceof long[])
        Arrays.fill((long[]) arreglo, val);
      return arreglo;
    }

    public <T> T[] nextObjectArray(Class<T> clazz, int size) {
      @SuppressWarnings("unchecked")
      T[] result = (T[]) java.lang.reflect.Array.newInstance(clazz, size);
      for (int c = 0; c < 3; c++) {
        Constructor<T> constructor;
        try {
          if (c == 0)
            constructor = clazz.getDeclaredConstructor(Scanner.class,
                Integer.TYPE);
          else if (c == 1)
            constructor = clazz.getDeclaredConstructor(Scanner.class);
          else
            constructor = clazz.getDeclaredConstructor();
        } catch (Exception e) {
          continue;
        }
        try {
          for (int i = 0; i < result.length; i++) {
            if (c == 0)
              result[i] = constructor.newInstance(this, i);
            else if (c == 1)
              result[i] = constructor.newInstance(this);
            else
              result[i] = constructor.newInstance();
          }
        } catch (Exception e) {
          throw new RuntimeException(e);
        }
        return result;
      }
      throw new RuntimeException("Constructor not found");
    }

    public Collection<Integer> wrap(int[] as) {
      ArrayList<Integer> ans = new ArrayList<Integer>();
      for (int i : as)
        ans.add(i);
      return ans;
    }

    public int[] unwrap(Collection<Integer> collection) {
      int[] vals = new int[collection.size()];
      int index = 0;
      for (int i : collection)
        vals[index++] = i;
      return vals;
    }

    int testCases = Integer.MIN_VALUE;

    boolean testCases() {
      if (testCases == Integer.MIN_VALUE) {
        testCases = nextInt();
      }
      return --testCases >= 0;
    }
  }

  static class SuperWriter {

    private final PrintWriter writer;

    public SuperWriter(OutputStream outputStream) {
      writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
    }

    public SuperWriter(Writer writer) {
        this.writer = new PrintWriter(writer);
    }

    public void close() {
        writer.flush();
        writer.close();
    }

    public void printLine(String line) {
      writer.println(line);
      if (!SHOULD_BUFFER_OUTPUT) {
        writer.flush();
      }
    }

    public void printLine(int... vals) {
      if (vals.length == 0) {
        writer.println();
      } else {
        writer.print(vals[0]);
        for (int i = 1; i < vals.length; i++)
          writer.print(" ".concat(String.valueOf(vals[i])));
        writer.println();
      }
      if (!SHOULD_BUFFER_OUTPUT) {
        writer.flush();
      }
    }

    public void printLine(long... vals) {
      if (vals.length == 0) {
        writer.println();
      } else {
        writer.print(vals[0]);
        for (int i = 1; i < vals.length; i++)
          writer.print(" ".concat(String.valueOf(vals[i])));
        writer.println();
      }
      if (!SHOULD_BUFFER_OUTPUT) {
        writer.flush();
      }
    }

    public void printLine(double... vals) {
      if (vals.length == 0) {
        writer.println();
      } else {
        writer.print(vals[0]);
        for (int i = 1; i < vals.length; i++)
          writer.print(" ".concat(String.valueOf(vals[i])));
        writer.println();
      }
      if (!SHOULD_BUFFER_OUTPUT) {
        writer.flush();
      }
    }

    public void printLine(int prec, double... vals) {
      if (vals.length == 0) {
        writer.println();
      } else {
        String precision = "%." + prec + "f";
        writer.print(String.format(precision, vals[0]).replace(',', '.'));
        precision = " " + precision;
        for (int i = 1; i < vals.length; i++)
          writer.print(String.format(precision, vals[i]).replace(',', '.'));
        writer.println();
      }
      if (!SHOULD_BUFFER_OUTPUT) {
        writer.flush();
      }
    }

    public <E> void printLine(Collection<E> vals) {
      if (vals.size() == 0) {
        writer.println();
      } else {
        int i = 0;
        for (E val : vals) {
          if (i++ == 0) {
            writer.print(val.toString());
          } else {
            writer.print(" ".concat(val.toString()));
          }
        }
        writer.println();
      }
      if (!SHOULD_BUFFER_OUTPUT) {
        writer.flush();
      }
    }

    public void printSimple(String value) {
      writer.print(value);
      if (!SHOULD_BUFFER_OUTPUT) {
        writer.flush();
      }
    }

    public boolean ifZeroExit(Number... values) {
    	for (Number number : values) {
    		if (number.doubleValue() != 0.0d || number.longValue() != 0) {
    			return false;
    		}
    	}
    	close();
    	System.exit(0);
    	return true;
    }
  }


  public static void main(String[] args) {
    main();
    sw.close();
  }
}
