#include <iostream>
#include <algorithm>
using namespace std;
typedef long long ll;

const int MAXN = 1e5 + 10;

int n;
struct ITEM {
  int a, b;
  int cnt;
} a[MAXN];
ll suma, sumb;

int main() {
  freopen("nit.in", "r", stdin);
  freopen("nit.out", "w", stdout);
  cin.tie(0)->sync_with_stdio(false), cout.tie(0);
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> a[i].a >> a[i].b;
    a[i].cnt = 2;
  }

  for (int i = 1; i <= n; ++i) {
    partial_sort(a + 1, a + 1, a + n + 1, [](ITEM x, ITEM y) {
      if (x.a != y.a) return x.a > y.a;
      return x.b < y.b;
    });
    suma += a[1].a;
    a[1].a = a[1].b, a[1].b = 0, a[1].cnt--;
    partial_sort(a + 1, a + 1, a + n + 1, [](ITEM x, ITEM y) {
      if (x.a != y.a) return x.a > y.a;
      return x.b < y.b;
    });
    sumb += a[1].a;
    a[1].a = a[1].b, a[1].b = 0, a[1].cnt--;
  }
  cout << suma - sumb << endl;
  return 0;
}