//Nguyen Huu Hoang Minh
/*
#include <bits/stdc++.h>
#define sz(x) int(x.size())
#define all(x) x.begin(),x.end()
#define reset(x) memset(x, 0,sizeof(x))
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define N 10005
#define remain(x) if (x > MOD) x -= MOD
#define ii pair<int, int>
#define iiii pair< ii , ii >
#define viiii vector< iiii >
#define vi vector<int>
#define vii vector< ii >
#define bit(x, i) (((x) >> (i)) & 1)
#define Task "test"
#define int long long

using namespace std;

typedef long double ld;
const int inf = 1e10;
const int minf = -1e10;

int n;
ii a[N];
int c[N];
int sum=0;
int f[N][N/2];

void readfile()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    if (fopen(Task".inp","r"))
    {
        freopen(Task".inp","r",stdin);
        //freopen(Task".out","w",stdout);
    }
    cin >> n;
    for(int i=n; i>=1; i--)
    {
        cin >> a[i].fi  >> a[i].se;
        c[i] = a[i].fi-a[i].se;
        sum += a[i].fi;
    }
}

void proc()
{
    //Gọi f[i][j] là chi phí chọn trợ lái khi xét từ người 1 đến i và chọn được j người.
    for(int i=1; i<=n; i++) f[i][0] = 0;
    for(int i=2; i<=n; i++){
        for(int j=1; j<=(i-1)/2; j++)
        {
            // không chọn i là thằng trợ lái -> f[i][j] = f[i-1][j]
            // chọn i là thằng trợ lái -> f[i][j] = f[i-1][j-1]+c[i]
            f[i][j] = max(f[i-1][j],f[i-1][j-1]+c[i]);
        }
        if (i%2==0) f[i][i/2] = f[i-1][i/2-1]+c[i];
    }
    cout << sum-f[n][n/2];
}

signed main()
{
    readfile();
    proc();
    return 0;
}
*/
#include <bits/stdc++.h>
#define sz(x) int(x.size())
#define all(x) x.begin(),x.end()
#define reset(x) memset(x, 0,sizeof(x))
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define N 10005
#define remain(x) if (x > MOD) x -= MOD
#define ii pair<int, int>
#define iiii pair< ii , ii >
#define viiii vector< iiii >
#define vi vector<int>
#define vii vector< ii >
#define bit(x, i) (((x) >> (i)) & 1)
#define Task "test"
#define int long long

using namespace std;

typedef long double ld;
const int inf = 1e10;
const int minf = -1e10;

int sum =0;
int n;
ii a[N];

void readfile()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    if (fopen(Task".inp","r"))
    {
        freopen(Task".inp","r",stdin);
        //freopen(Task".out","w",stdout);
    }
    cin >> n;
    for(int i=1; i<=n; i++)
    {
        cin >> a[i].fi >> a[i].se;
        sum += a[i].fi;
    }
}

void proc()
{
    priority_queue<int> q;
    int ans = 0;
    for(int i=1; i<n; i++)
    {
        q.push(a[i].fi-a[i].se);
        if (i%2!=0)
        {
            ans += q.top();
            q.pop();
        }
    }
    cout << sum-ans;
}

signed main()
{
    readfile();
    proc();
    return 0;
}