#include <bits/stdc++.h>
#define fast_input_output() ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr)
typedef long long ll;
using namespace std;
int main() {
fast_input_output();
ll n; cin >> n;
vector<pair<ll, ll>> v(n);
for (int i = 0; i < n; i++) cin >> v[i].first >> v[i].second;
sort(v.begin(), v.end());
ll arr[n]; arr[0] = v[0].second;
for (int i = 1; i < n; i++) {
ll x = arr[i-1] + v[i-1].first - v[i].first + v[i].second;
arr[i] = max(x, v[i].second);
}
ll ans = LLONG_MIN;
for (int i = 0; i < n; i++) ans = max(ans, arr[i]);
cout << ans;
return 0;
}
