#include <bits/stdc++.h>
using namespace std;
struct Artwork {
long long size, value;
bool operator < (const Artwork &other) const {
return size < other.size;
}
};
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int length;
cin >> length;
vector works = {Artwork{0, 0}};
for (int index = 0; index < length; index++) {
long long size, value;
cin >> size >> value;
works.push_back(Artwork{size, value});
}
sort(works.begin(), works.end());
vector<long long> prefix_value_sums;
long long total = 0;
for (Artwork work: works) {
total += work.value;
prefix_value_sums.push_back(total);
}
vector<long long> suffix_maximas(length + 1);
suffix_maximas.back() = prefix_value_sums.back() - works.back().size;
for (int index = length - 1; index > 0; index--) {
suffix_maximas[index] = max(suffix_maximas[index + 1], prefix_value_sums[index] - works[index].size);
}
long long maxima = -1LL;
for (int index = 1; index <= length; index++) {
maxima = max(maxima, works[index].size - prefix_value_sums[index - 1] + suffix_maximas[index]);
}
cout << maxima << "\n";
return 0;
}
