#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
int n;
cin >> n;
vector<pair<long long,long long>> v;
v.reserve(n);
for (int i = 0; i < n; ++i) {
long long a, b;
cin >> a >> b;
v.push_back({a, b});
}
ranges::sort(v);
long long prefix = 0;
long long ans = LLONG_MIN;
long long min_val = LLONG_MAX;
for (auto &p : v) {
long long a = p.first;
long long b = p.second;
long long val = prefix - a;
if (val < min_val) {
min_val = val;
}
prefix += b;
if (long long curr = prefix - a - min_val; curr > ans) {
ans = curr;
}
}
cout << ans << endl;
return 0;
}
