#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll, ll>
#define fi first
#define se second
const ll MX = 5e5 + 10;
ll N, pref[MX];
vector<pii> vec;
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> N;
for(int i = 0; i < N; i++){
ll x, y; cin >> x >> y;
vec.push_back({x, y});
}
sort(vec.begin(), vec.end());
pref[0] = vec[0].se;
for(int i = 1; i < N; i++) pref[i] = pref[i - 1] + vec[i].se;
priority_queue<ll> pq;
ll ans = 0;
for(int i = N - 1; i >= 0; i--){
pq.push(pref[i] - vec[i].fi);
ans = max(ans, pq.top() - (i == 0 ? 0 : pref[i - 1]) + vec[i].fi);
}
cout << ans << '\n';
}
