#include<bits/stdc++.h>
#define MAXN 100010
#define ll long long
using namespace std;

struct node{
	int a,b;
}p[MAXN];
bool cmp(node x,node y){return x.a+x.b>y.a+y.b;}
ll n,suma,sumb;

int main(){
	freopen("nit.in","r",stdin);
	freopen("nit.out","w",stdout);
	cin>>n;
	for(int i=1;i<=n;++i) cin>>p[i].a>>p[i].b;
	sort(p+1,p+n+1,cmp);
	suma=0; sumb=0;
	for(int i=1;i<=n;++i)
	{
		if(i%2)
		{
			suma+=p[i].a;
			sumb+=p[i].b;
		}
		else
		{
			sumb+=p[i].a;
			suma+=p[i].b;
		}
	}
	cout<<suma-sumb<<endl;
	return 0;
}