#include <iostream>
#include <algorithm>
#include <vector>
#include <set>
using namespace std;
#define int long long
const int maxn = 100'001;
const int inf = 1e18;
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n;
cin >> n;
vector<pair<int, int>> vec(n);
for (int i = 0; i < n; ++i) {
cin >> vec[i].first >> vec[i].second;
}
sort(vec.begin(), vec.end());
int mx = -inf;
int sum = 0;
int ans = 0;
for (auto [a, s] : vec) {
mx = max(mx, a - sum);
sum += s;
ans = max(ans, sum - a + mx);
}
cout << ans << '\n';
}
// a[i] - p[i] -> max
