#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<ll, ll>;
const int MOD = 998244353;
struct SegTree {
vector<ll> tree;
SegTree(int n) {
tree.assign(4*n, -1e18);
}
void query(int p, int l, int r, int i, ll x) {
if (l>i||r<i) {
return;
}
if (l==r) {
tree[p] = x;
}
else {
int m = (l+r)/2;
query(2*p, l, m, i, x);
query(2*p+1, m+1, r, i, x);
tree[p] = max(tree[2*p], tree[2*p+1]);
}
}
ll rmq(int p, int l, int r, int i, int j) {
if (l>j || r<i) return -1e18;
if (i<=l && r<=j) return tree[p];
int m = (l+r)/2;
return max(rmq(2*p, l, m, i, j), rmq(2*p+1, m+1, r, i, j));
}
};
void solve() {
int n; cin >> n;
vector<pii> a(n);
SegTree st(n);
for (int i=0; i<n; i++) {
cin >> a[i].first >> a[i].second;
}
sort(a.begin(), a.end());
vector<ll> pref(n, 0);
pref[0] = a[0].second;
for (int i=1; i<n; i++) {
pref[i] = pref[i-1] + a[i].second;
}
for (int i=0; i<n; i++) {
st.query(1, 0, n-1, i, pref[i]-a[i].first);
}
ll ans=0;
for (int i=0; i<n; i++) {
ll mx = st.rmq(1, 0, n-1, i, n-1);
ll restar = (i==0 ? 0 : pref[i-1]);
ans = max(ans, mx+a[i].first-restar);
}
cout << ans << "\n";
}
//1 2 3 4 0
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int t=1;
while (t--) {
solve();
}
return 0;
}
