There are N dishes of cuisine placed in front of Takahashi and Aoki. For convenience, we call these dishes Dish 1, Dish 2, ..., Dish N.

When Takahashi eats Dish i, he earns A_i points of happiness; when Aoki eats Dish i, she earns B_i points of happiness.

Starting from Takahashi, they alternately choose one dish and eat it, until there is no more dish to eat. Here, both of them choose dishes so that the following value is maximized: "the sum of the happiness he/she will earn in the end" minus "the sum of the happiness the other person will earn in the end".

Find the value: "the sum of the happiness Takahashi earns in the end" minus "the sum of the happiness Aoki earns in the end".

Constraints

* 1 \leq N \leq 10^5
* 1 \leq A_i \leq 10^9
* 1 \leq B_i \leq 10^9
* All values in input are integers.

Input

Input is given from Standard Input in the following format:


N
A_1 B_1
:
A_N B_N


Output

Print the value: "the sum of the happiness Takahashi earns in the end" minus "the sum of the happiness Aoki earns in the end".

Examples

Input

3
10 10
20 20
30 30


Output

20


Input

3
20 10
20 20
20 30


Output

20


Input

6
1 1000000000
1 1000000000
1 1000000000
1 1000000000
1 1000000000
1 1000000000


Output

-2999999997
import java.util.*;
import java.io.*;
import java.math.*;
public class Main
{
    static class Reader 
    { 
        private InputStream mIs;private byte[] buf = new byte[1024];private int curChar,numChars;public Reader() { this(System.in); }public Reader(InputStream is) { mIs = is;} 
        public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];} 
        public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;} 
        public String s(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();} 
        public long l(){int c = read();while (isSpaceChar(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 *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;} 
        public int i(){int c = read() ;while (isSpaceChar(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 *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;} 
        public double d() throws IOException {return Double.parseDouble(s()) ;}
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; } 
        public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; } 
        public int[] arr(int n){int[] ret = new int[n];for (int i = 0; i < n; i++) {ret[i] = i();}return ret;}
    }
    
    
 
           //       |----|       /\      |    |   -----   |
           //       |   /       /  \     |    |     |     |
           //       |--/       /----\    |----|     |     |
           //       |   \     /      \   |    |     |     |
           //       |    \   /        \  |    |   -----   -------
    static class B1 implements Comparable<B1>
    {
        int x;int y;int index;
        public B1(int a,int b,int c) 
        {
            x=a;
            y=b;
            index =c;
        }
        public int compareTo(B1 num) 
        {
            if(x-num.y>num.x-y)
            return -1;
            return 1;
        }
    }
    static class B implements Comparable<B>
    {
        int x;int y;int index;
        public B(int a,int b,int c) 
        {
            x=a;
            y=b;
            index =c;
        }
        public int compareTo(B num) 
        {
            if(y-num.x>num.y-x)
            return -1;
            return 1;
        }
    }
    public static void main(String[] args)throws IOException
    {
        PrintWriter out= new PrintWriter(System.out);
        Reader sc=new Reader();
        int n=sc.i();
        B1 arr[]=new B1[n];
        B brr[]=new B[n];
        for(int i=0;i<n;i++)
        {
            arr[i]=new B1(sc.i(),sc.i(),i);
            brr[i]=new B(arr[i].x,arr[i].y,i);
        }
        Arrays.sort(arr);
        Arrays.sort(brr);
        int c=0;
        long ans=0;
        int i=0,j=0;
        int mark[]=new int[n];
        int count=0;
        while(count!=n)
        {
            if(c==0)
            {
                while(mark[arr[i].index]!=0)
                i++;
                mark[arr[i].index]=1;
                ans+=(long)arr[i].x;
                i++;
            }
            else
            {
                while(mark[brr[j].index]!=0)
                j++;
                mark[brr[j].index]=1;
                ans-=(long)brr[j].y;
                j++;
            }
            count++;
            c^=1;
        }
        out.println(ans);
        out.flush();
    }
}