#include <bits/stdc++.h>
using namespace std;
using ll = long long;
struct SegTree {
int n;
vector<ll> st;
SegTree(int _n) : n(_n), st(4 * n, LLONG_MAX) {}
void build(int p, int l, int r, const vector<ll> &a) {
if (l == r) st[p] = a[l];
else {
int m = (l + r) >> 1;
build(p << 1, l, m, a);
build(p << 1 | 1, m + 1, r, a);
st[p] = min(st[p << 1], st[p << 1 | 1]);
}
}
ll query(int p, int l, int r, int i, int j) {
if (j < l || r < i) return LLONG_MAX;
if (i <= l && r <= j) return st[p];
int m = (l + r) >> 1;
return min(query(p << 1, l, m, i, j), query(p << 1 | 1, m + 1, r, i, j));
}
};
int main() {
int n; cin >> n;
vector<pair<ll, ll>> a(n);
for (int i = 0; i < n; i++) cin >> a[i].first >> a[i].second;
sort(a.begin(), a.end(), [](auto &x, auto &y) { return x.first < y.first; });
vector<ll> p(n + 1);
for (int i = 1; i <= n; i++) p[i] = p[i - 1] + a[i - 1].second;
vector<ll> m(n + 1);
for (int i = 1; i <= n; i++) m[i] = p[i - 1] - a[i - 1].first;
SegTree st(n + 1);
st.build(1, 1, n, m);
ll ans = LLONG_MIN;
for (int i = 1; i <= n; i++) {
ll m1 = st.query(1, 1, n, 1, i);
ll m2 = (p[i] - a[i - 1].first) - m1;
ans = max(ans, m2);
}
cout << ans;
}
