#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fro for
#define pb push_back
#define ld long double
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n;
cin >> n;
vector<pair<int, int>> C(n);
for (int i = 0; i < n; i++) cin >> C[i].first >> C[i].second;
sort(C.begin(), C.end());
vector<int> A(n);
vector<int> B(n);
for (int i = 0; i < n; i++) {
A[i] = C[i].first;
B[i] = C[i].second;
}
vector<int> prefb(n);
prefb[0] = B[0];
for (int i = 1; i < n; i++) {
prefb[i] = prefb[i - 1] + B[i];
}
vector<int> C1(n), D(n);
C1[0] = A[0];
D[0] = prefb[0]-A[0];
fro (int i = 1; i < n; i++) {
C1[i] = A[i] - prefb[i - 1];
D[i] = prefb[i] - A[i];
}
for (int i = n - 2; i >= 0; i--) {
D[i] = max(D[i], D[i + 1]);
}
int ans = 0;
for (int i = 0; i < n; i++) {
ans = max(ans, C1[i] + D[i]);
}
cout << ans;
}
