#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define el cout << "\n"
#define sz(x) (long long)(x).size()
#define all(x) (x).begin(), (x).end()
#define pii pair<int, int>
using ll = long long;
#define int long long
#define FOR(i, a, b) for (int i = a; i <= b; i++)
const long long mx3 = 6e5 + 1, mod = 1e9 + 7 ;
long long pre[mx3],b[mx3] , BrunoFernandes,n,k,m,q ;
ll dp[mx3] ;
void RubenAmorim()
{
cin >> n ;
vector < pii > a(n) ;
FOR(i, 0, n - 1) {
cin >> a[i].fi >> a[i].se;
}
sort(all(a));
vector<ll> pre(n + 1, 0);
FOR(i, 1, n)
pre[i] = pre[i - 1] + a[i - 1].se;
ll ans = 0, mx = 0;
FOR(i, 1, n)
{
mx = max(mx, -pre[i - 1] + a[i - 1].fi);
ll tmp = pre[i] - a[i - 1].fi + mx;
ans = max(ans, tmp);
}
cout << ans ;
}
signed main()
{
//freopen("DEQUY7.INP", "r", stdin);
//freopen("DEQUY7.OUT", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie (0); cout.tie(0);
BrunoFernandes = 1;
//cin >> BrunoFernandes;
while (BrunoFernandes--)
RubenAmorim();
}
