#include <iostream>
#include <vector>
#include <algorithm>
#include <unordered_set>
#include <cstring>
#include <array>
#include <cmath>
#include <stack>
#include <queue>
#include <map>
#include <set>
#define INF 1e18
using namespace std;
typedef long long ll;
const ll MOD = 1000000007;
const ll MAXN = 1005;
void solve()
{
int n; cin >> n;
vector<pair<ll, ll>>v(n + 1);
for (int i = 1; i <= n; i++)cin >> v[i].first >> v[i].second;
sort(v.begin(), v.end());
ll ans = 0, sum = 0, mx = -INF;
for (int i = 1; i <= n; i++) {
mx = max(mx, -sum + v[i].first);
sum += v[i].second;
ans = max(ans, mx + sum - v[i].first);
}
cout << ans << "\n";
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;// cin >> t;
while (t--) solve();
return 0;
}
