import std.stdio, std.string, std.conv;
import std.range, std.algorithm, std.array, std.typecons, std.container;
import std.math, std.numeric, core.bitop;

enum inf3 = 1_001_001_001;
enum inf6 = 1_001_001_001_001_001_001L;
enum mod = 1_000_000_007L;

alias R = Tuple!(long, "a", long, "b");

void main() {
    int n;
    scan(n);
    auto r = new R[](n);
    foreach (i ; 0 .. n) {
        int a, b;
        scan(a, b);
        r[i] = R(a, b);
    }

    r.sort!"a.a + a.b > b.a + b.b"();

    debug {
        foreach (i ; 0 .. n) {
            writeln(r[i]);
        }
    }

    long ans;

    foreach (i ; 0 .. n) {
        if (i % 2 == 0) {
            ans += r[i].a;
        }
        else {
            ans -= r[i].b;
        }
    }

    writeln(ans);
}






void scan(T...)(ref T args) {
    import std.stdio : readln;
    import std.algorithm : splitter;
    import std.conv : to;
    import std.range.primitives;

    auto line = readln().splitter();
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront();
    }
    assert(line.empty);
}

void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}
