acwing 125

#include <bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0)
#define _zero(a) memset(a, 0, sizeof(a))
#define endl '\n'
#define int long long
#define mp make_pair
#define PII pair<int, int>
#define x first
#define y second
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define PII pair<int, int>
typedef long long ll;
typedef double dd;
typedef long double ld;

using namespace std;

const int inf = 1e10;
const int M = 998244353;
const ld pi = atan2(0, -1);//arctan(y/x);
const ld eps = 1e-8;

const int maxn = 5e4 + 100;

int n;
PII a[maxn];
int sum[maxn];

bool cmp(PII a1, PII a2)
{
    return a2.x - a1.y < a1.x - a2.y;
}

signed main()
{
    IOS;
    cin >> n;
    for(int i = 1; i <= n; i++){
        cin >> a[i].x;
        cin >> a[i].y;
    }
    sort(a + 1, a + 1 + n, cmp);
    sum[n] = 0;
    for(int i = n - 1; i >= 1; i--) sum[i] = sum[i + 1] + a[i + 1].x;
    int mx = -1e10;
    for(int i = 1; i <= n; i++) mx = max(mx, sum[i] - a[i].y);
    cout << mx;
    return 0;
}