#include<bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin >> n;
vector<pair<long long,long long>> a(n);
for(int i = 0; i < n; i++){
cin >> a[i].first >> a[i].second;
}
sort(a.begin(), a.end());
vector<long long> pref(n + 1, 0);
for(int i = 1; i <= n; i++){
pref[i] =
pref[i-1] + a[i-1].second;
}
long long ans = 0;
long long best =
pref[0] - a[0].first;
for(int r = 1; r <= n; r++){
long long cur =
pref[r]
- a[r-1].first
- best;
ans = max(ans, cur);
best =
min(
best,
pref[r-1] - a[r-1].first
);
}
cout << ans << '\n';
return 0;
}
