#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) x.begin(), x.end()
#define size(x) (int)x.size()
template<class S, class T>
bool chmin(S &a, const T &b) {
return a > b && (a = b) == b;
}
template<class S, class T>
bool chmax(S &a, const T &b) {
return a < b && (a = b) == b;
}
const int inf = 1e9 + 7;
const int INF = 1e18 + 7;
const int mod = 1e9 + 7;
signed main() {
cin.tie(nullptr)->sync_with_stdio(false);
int n; cin >> n;
int a[n], b[n];
vector<pair<int, int>> v;
for (int i = 0; i < n; ++i) {
cin >> a[i] >> b[i];
v.push_back({a[i], b[i]});
}
sort(all(v));
for (int i = 0; i < n; ++i) a[i] = v[i].first, b[i] = v[i].second;
int res = b[0], pref = b[0], min = -a[0];
for (int i = 1; i < n; ++i) {
chmin(min, pref - a[i]);
pref += b[i];
chmax(res, pref - min - a[i]);
}
cout << res;
}
