#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
int N;
cin >> N;
vector<ll> A(N), B(N);
for (int i = 0; i < N; i++) {
cin >> A[i] >> B[i];
}
vector<int> idx(N);
iota(begin(idx), end(idx), 0);
sort(begin(idx), end(idx), [&](int i, int j) { return A[i] < A[j]; });
vector<ll> pf(N); pf[0] = 0;
for (int i = 1; i < N; i++) {
pf[i] = pf[i - 1] + B[idx[i]] + A[idx[i - 1]] - A[idx[i]];
}
vector<ll> sf(N); sf[N - 1] = pf[N - 1];
for (int i = N - 1; i > 0; i--) {
sf[i - 1] = max(pf[i - 1], sf[i]);
}
ll ans = 0;
for (int i = 0; i < N; i++) {
ans = max(ans, sf[i] - pf[i] + B[idx[i]]);
}
cout << ans << '\n';
return 0;
}
