#include <bits/stdc++.h>
//#define int long long */
#define ll long long
#define fi first
#define se second
#define ve vector
using namespace std;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
#define all(x) x.begin(), x.end()
const int MAXN = 3e5+10;
signed main(){
int n;
cin >> n;
ve<pll> v(n);
for(auto& i : v)
cin >> i.fi >> i.se;
sort(all(v));
ll res = LLONG_MIN;
ll sum = 0;
ll mx = 0;
for(int i = 0; i < n; i++){
mx = max(mx, v[i].fi - sum);
sum += v[i].se;
res = max(res, mx + sum - v[i].fi);
}
cout << res << "\n";
}
