// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>
using namespace std;
#define nl '\n'
#define pb push_back
using ll = long long;
template<class T> using V = vector<T>;
using vi = V<int>;
using vl = V<ll>;
const ll INFL = 2e18;
int main() {
cin.tie(0)->sync_with_stdio(0);
int N; cin >> N;
vl A(N), B(N); for(int i = 0; i < N; i++) cin >> A[i] >> B[i];
vi ord(N); iota(begin(ord), end(ord), 0);
sort(begin(ord), end(ord), [&](int x, int y) {
return A[x] < A[y];
});
vl P = {0}; for(auto& i : ord) P.pb(P.back() + B[i]);
ll ans = 0, mn = INFL;
for(int i = 0; i <= N; i++) {
if (i != 0) {
ans = max(P[i] - A[ord[i - 1]] - mn, ans);
}
if (i != N) mn = min(P[i] - A[ord[i]], mn);
}
cout << ans << nl;
exit(0-0);
}
