#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
int n;
int a, b, ansa, ansb, f = 1;
priority_queue<pair<int ,pair<int, int>> >q;
int main(){
    freopen("nit.in", "r", stdin);
    freopen("nit.out", "w", stdout);
    cin >> n;
    for(int i = 1;i <= n;i++){
        cin >> a >> b;
        q.push({a - b, {a, b}});
    }
    while(!q.empty()){
        auto now = q.top();q.pop();
        if(now.second.first != 0){
            if(f == 1){
                ansa += now.second.first;
                q.push({now.second.second, {0, now.second.second}});
                f = 0;
            } 
            else{
                ansb += now.second.first;;
                q.push({now.second.second, {0, now.second.second}});
                f = 1;
            }
        }
        else{
            if(f == 1){
                ansa += now.second.second;
                f = 0;
            }
            else{
                ansb += now.second.second;
                f = 1;
            }
        }
    }
    cout<<ansa - ansb<<endl;
    return 0; 
}