#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<ll> vi;
typedef pair<ll, ll> pi;
#define FOR(i, j, k) for (ll i = j; i < (ll) k; ++i)
#define FORD(i, j, k) for (ll i = j; i >= (ll) k; --i)
#define nl "\n"
#define all(x) (x).begin(), (x).end()
#define sc second
#define fr first
#define pb push_back
const ll inf = 1e18 + 5;
void solve()
{
ll n;
cin >> n;
pi a[n + 1] = {};
FOR(i, 1, n + 1)
cin >> a[i].fr >> a[i].sc;
sort(a + 1, a+n+1);
// FOR(i, 1, n + 1) {
// cout << a[i].fr << " " << a[i].sc << nl;
// }
ll sum[n + 1] = {};
FOR(i, 1, n + 1) {
sum[i] = sum[i - 1] + a[i].sc;
}
ll ans = a[1].sc;
ll mn = sum[0] - a[1].fr;
FOR(i, 2, n + 1) {
mn = min(mn, sum[i - 1] - a[i].fr);
ans = max(ans, sum[i] - a[i].fr - mn);
}
cout << ans << nl;
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll t = 1;
// cin >> t;
while (t--)
{
solve();
}
}
