#include <bits/stdc++.h>
#define int long long
using namespace std;

const int N = 100010;
int n, a, b, ans1, ans2;
struct node{
	int x, y;
	bool friend operator <(node u, node v) {
		if (u.x == v.x) return (u.x - u.y) < (v.x - v.y);
		return u.x < v.x;
	}
};
priority_queue <node> q;

signed main() {
	freopen("nit.in", "r", stdin);
	freopen("nit.out", "w", stdout);
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> a >> b;
		q.push({a, b});
	}
	for (int i = 1; i <= 2 * n; i++) {
		node t = q.top();
		q.pop();
		if (i % 2) ans1 += t.x;
		else ans2 += t.x;
		q.push({t.y, 0});
	}
	cout << ans1 - ans2;
	return 0;
}