#include "bits/stdc++.h"
using namespace std;
struct node {
long long s, e, m, val;
node *l, *r;
node (long long _s, long long _e) {
s = _s;
e = _e;
m = (s + e)/2;
val = 0;
if (s == e) return;
l = new node(s, m);
r = new node(m+1, e);
}
void upd(long long p, long long v) {
if (s == p && s== e) {
val = v;
return;
}
if (p <= m) {
l->upd(p, v);
}
else {
r->upd(p, v);
}
val = l->val + r->val;
}
long long qry(long long qs, long long qe) {
if (qs <= s && e <= qe) {
return val;
}
else if (qs > e || s > qe) {
return 0;
}
else {
return l->qry(qs, qe) + r->qry(qs, qe);
}
}
} *root;
void init(long long N) {
root = new node(0, N-1);
}
void update(long long P, long long V) {
root->upd(P, V);
}
long long query(long long A, long long B) {
return root->qry(A, B);
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
long long n;
cin >> n;
vector<pair<long long, long long> > works;
for (long long i=0; i<n; i++) {
long long siz, val;
cin >> siz >> val;
works.push_back(make_pair(siz, val));
}
sort(works.begin(), works.end());
init(n);
for (long long i=0; i<n; i++) {
update(i, works[i].second);
}
long long best = LLONG_MIN;
for (long long i=0; i<n; i++) {
for (long long j=i; j<n; j++) {
best = max(best, query(i, j) + works[i].first - works[j].first);
}
}
cout << best << endl;
}
