#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define l(a, b, i) for (ll i = a; i < b; i++)
#define rl(a, b, i) for (ll i = a; i >= b; i--)
#define vpair vector<pair<ll, ll>>
#define inf LLONG_MAX
#define ninf LLONG_MIN
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
ll N; cin >> N; vector<ll> sz(N + 1, 0), val(N + 1, 0); vector<pair<ll, ll>> vec(N + 1);
l(1, N + 1, i) {
cin >> sz[i] >> val[i];
vec[i] = {sz[i], val[i]};
}
sort(vec.begin() + 1, vec.end()); // sort theo increasing size nhé
vector<ll> pre(N + 1, 0); // prefix cái val á
l(1, N + 1, i) pre[i] = pre[i - 1] + vec[i].second;
ll ans = ninf;
ll curmin = vec[1].first;
l(1, N + 1, i) {
ans = max(ans, pre[i] - vec[i].first + curmin);
if (i + 1 <= N) curmin = max(curmin, vec[i + 1].first - pre[i]);
}
cout << ans;
}
