#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
 
#define pb push_back
#define mk make_pair
#define ff first
#define ss second
#define fast ios::sync_with_stdio(false);cin.tie(0);
 
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef tree<int, null_type, less<int>,
        rb_tree_tag, tree_order_statistics_node_update> ordered_set; // CUR


int main(){
	fast
	
	int n;
	cin>>n;
	int a[n],b[n];
	ll mx = 0;
	vector<int> v;
	for(int i=0;i<n;i++){
		cin>>a[i]>>b[i];
		mx += a[i];
		v.pb(b[i] - a[i]);
		}
	sort(v.begin(),v.end());
	reverse(v.begin(), v.end());
	
	for(int i=0;i<n/2;i++)
		mx += v[i];
	
	cout<<mx<<endl;
	
	
return 0;
}