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.io.*;
import java.util.Arrays;
import java.util.Comparator;
import java.util.StringJoiner;
import java.util.StringTokenizer;
import java.util.function.Function;

public class Main {

    static int N;
    static Entry[] E;

    public static void main(String[] args) {
        FastScanner sc = new FastScanner(System.in);
        N = sc.nextInt();
        E = new Entry[N];
        for (int i = 0; i < N; i++) {
            E[i] = new Entry(sc.nextInt(), sc.nextInt());
        }

        System.out.println(solve());
    }

    static long solve(int n, int[] A, int[] B) {
        N = n;
        E = new Entry[N];
        for (int i = 0; i < N; i++) {
            E[i] = new Entry(A[i], B[i]);
        }
        return solve();
    }

    static long solve() {
        Entry[] TAK = new Entry[N];
        Entry[] AOK = new Entry[N];
        for (int i = 0; i < N; i++) {
            TAK[i] = E[i];
            AOK[i] = E[i];
        }
        Arrays.sort(TAK, (e1, e2) -> {
            int u = e1.a - e2.b;
            int v = e2.a - e1.b;
            return Integer.compare(v, u);
        });

        Arrays.sort(AOK, (e1, e2) -> {
            int u = e1.b - e2.a;
            int v = e2.b - e1.a;
            return Integer.compare(v, u);
        });

        long totalTak = 0;
        long totalAok = 0;
        int taki = 0;
        int aoki = 0;
        for (int i = 0; i < N; i++) {
            if( i % 2 == 0 ) {
                if( TAK[taki].used ) taki++;

                totalTak += TAK[taki].a;
                TAK[taki].used = true;
                taki++;
            } else {
                if( AOK[aoki].used ) aoki++;

                totalAok += AOK[aoki].b;
                AOK[aoki].used = true;
                aoki++;
            }
        }
        return totalTak - totalAok;
    }

    static class Entry {
        int a, b;
        boolean used;

        public Entry(int a, int b) {
            this.a = a;
            this.b = b;
        }
    }

    @SuppressWarnings("unused")
    static class FastScanner {
        private BufferedReader reader;
        private StringTokenizer tokenizer;

        FastScanner(InputStream in) {
            reader = new BufferedReader(new InputStreamReader(in));
            tokenizer = null;
        }

        String next() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        String nextLine() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    return reader.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken("\n");
        }

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

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

        int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        int[] nextIntArray(int n, int delta) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt() + delta;
            return a;
        }

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

    static <A> void writeLines(A[] as, Function<A, String> f) {
        PrintWriter pw = new PrintWriter(System.out);
        for (A a : as) {
            pw.println(f.apply(a));
        }
        pw.flush();
    }

    static void writeLines(int[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (int a : as) pw.println(a);
        pw.flush();
    }

    static void writeLines(long[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (long a : as) pw.println(a);
        pw.flush();
    }

    static int max(int... as) {
        int max = Integer.MIN_VALUE;
        for (int a : as) max = Math.max(a, max);
        return max;
    }

    static int min(int... as) {
        int min = Integer.MAX_VALUE;
        for (int a : as) min = Math.min(a, min);
        return min;
    }

    static void debug(Object... args) {
        StringJoiner j = new StringJoiner(" ");
        for (Object arg : args) {
            if (arg instanceof int[]) j.add(Arrays.toString((int[]) arg));
            else if (arg instanceof long[]) j.add(Arrays.toString((long[]) arg));
            else if (arg instanceof double[]) j.add(Arrays.toString((double[]) arg));
            else if (arg instanceof Object[]) j.add(Arrays.toString((Object[]) arg));
            else j.add(arg.toString());
        }
        System.err.println(j.toString());
    }
}
