// #pragma optimize ("g",on)
// #pragma GCC optimize ("inline")
// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC optimize ("03")
#include <bits/stdc++.h>
#define pb push_back
#define SS ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
#define int long long
#define all(v) v.begin(),v.end()
using namespace std;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 4e5 + 1, inf = 1e9 + 1, mod = 998244353;
void solve(){
int n;
cin >> n;
pair<int, int> p[n + 1];
for(int i = 1; i <= n; i++){
cin >> p[i].first >> p[i].second;
}
sort(p + 1, p + n + 1);
int mx = 0, sum = 0, ans = 0;
for(int i = 1; i <= n; i++){
mx = max(mx, p[i].first - sum);
ans = max(ans, mx - p[i].first + sum + p[i].second);
sum += p[i].second;
}
cout << ans;
}
signed main(){
SS
// freopen("trains.in", "r", stdin);
// freopen("trains.out", "w", stdout);
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
