#include <iostream>
#include <algorithm>
#include <vector>
#include <climits>
using namespace std;
struct Artwork {
long long a;
int b;
bool operator < (const Artwork& other) const {
return a < other.a;
}
};
int main()
{
int n;
cin >> n;
vector < Artwork > gallery(n + 1);
for (int i = 1; i <= n; ++i) {
cin >> gallery[i].a >> gallery[i].b;
}
sort(gallery.begin() + 1, gallery.end());
vector < long long > bPartialSums(n + 1);
for (int i = 1; i <= n; ++i) {
bPartialSums[i] = bPartialSums[i - 1] + gallery[i].b;
}
vector < long long > suffixMax(n + 2);
for (int i = n; i > 0; --i) {
suffixMax[i] = max(suffixMax[i + 1], bPartialSums[i] - gallery[i].a);
}
long long ans = LLONG_MIN;
for (int i = 1; i <= n; ++i) {
ans = max(ans, suffixMax[i] + gallery[i].a - bPartialSums[i - 1]);
}
cout << ans << '\n';
return 0;
}
