#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
#include <set>
#include <climits>
#include <cmath>
#include <fstream>
#include <queue>
using namespace std;
int main(){
int n;
cin >> n;
vector<pair<long long, long long>> art;
for (int i = 0; i < n; i++) {
long long a, b;
cin >> a >> b;
art.push_back(make_pair(a, b));
}
sort(art.begin(), art.end());
vector<long long> pre(n + 1);
pre[0] = 0;
vector<long long> diff(n + 1);
diff[0] = 0;
for (int i = 0; i < n; i++) {
pre[i + 1] = pre[i] + art[i].second;
diff[i + 1] = pre[i + 1] - art[i].first;
}
vector<long long> maxes(n + 1);
for (int i = n; i > 0; i--) {
if (i == n) {
maxes[i] = diff[i];
}
else {
maxes[i] = max(maxes[i + 1], diff[i]);
}
}
maxes[0] = 0;
long long best = 0;
for (int i = 1; i <= n; i++) {
long long cur = art[i - 1].first;
cur += maxes[i] - pre[i - 1];
best = max(best, cur);
}
cout << best << endl;
}
