#include<bits/stdc++.h>
using namespace std;
#define i64 long long
#define mp make_pair
#define pb push_back
#define all(x) (x).begin(), (x).end()
struct Tree{
int n;
vector<int64_t>lazy;
vector<int64_t>st;
Tree(int _n, int64_t _v): n(_n), st(_n * 4, _v), lazy(_n * 4, _v){};
void push(int id){
int64_t add = lazy[id];
lazy[id * 2] += add, st[id * 2] += add;
lazy[id * 2 + 1] += add, st[id * 2 + 1] += add;
lazy[id] = 0;
}
void update(int id, int l, int r, int u, int v, int64_t val){
if (v < l || u > r) return;
if (u <= l && r <= v) {
st[id] = val;
// lazy[id] += val;
return;
}
// push(id);
int mid = (l + r)/2;
update(id * 2, l, mid, u, v, val);
update(id * 2 + 1, mid + 1, r, u, v, val);
st[id] = max(st[id * 2], st[id * 2 + 1]);
}
i64 get(int id, int l, int r, int u, int v) {
if (v < l || u > r) return -1000000000000000000;
if (u <= l && r <= v) return st[id];
int mid = (l + r)/2;
return max(get(id * 2, l, mid, u, v), get(id * 2 + 1, mid + 1, r, u, v));
}
};
void Solve(void) {
int N; cin >> N;
Tree sum(N + 5, 0);
vector<pair<i64, i64>> pictures(N);
vector<i64> pref(N + 5, 0);
for (int i = 0; i < N; i ++) {
cin >> pictures[i].first >> pictures[i].second;
}
sort(all(pictures));
for (int i = 0; i < N; i ++) {
pref[i + 1] = pref[i] + pictures[i].second;
sum.update(1, 1, N, i + 1, i + 1, pref[i + 1] - pictures[i].first);
}
i64 ans = LLONG_MIN;
for (int i = 1; i <= N; i ++) {
ans = max(ans, sum.get(1, 1, N, i, N) - pref[i - 1] + pictures[i - 1].first);
}
cout << ans << "\n";
}
signed main() {
ios_base::sync_with_stdio(false); cin.tie(0);
int Tests = 1; // cin >> Tests;
while (Tests --) {
Solve();
}
}
