// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>
using namespace std;
#define nl '\n'
using ll = long long;
int main() {
cin.tie(0)->sync_with_stdio(0);
int N; cin >> N;
vector<ll> A(N); vector<int> B(N);
for(int i = 0; i < N; i++) cin >> A[i] >> B[i];
vector<int> I(N); iota(begin(I), end(I), 0);
sort(begin(I), end(I), [&](int x, int y) {
return A[x] < A[y];
});
vector<ll> P(N);
for(int i = 0; i < N; i++) {
P[i] += -A[I[i]] + B[I[i]];
if (i+1 < N) P[i+1] += A[I[i]];
}
for(int i = 1; i < N; i++) P[i] += P[i-1];
ll ans = 0, S = 0;
vector<ll> mx = P; for(int i = N-2; i >= 0; i--) mx[i] = max(mx[i], mx[i+1]);
for(int i = 0; i < N; i++) {
ll res = mx[i] - S + A[I[i]]; S += B[I[i]];
ans = max(ans, res);
}
cout << ans << nl;
return 0;
}
