#include<bits/stdc++.h>
using namespace std;
int n;
pair<long long, long long> a[500001];
long long pre1[500001], pre2[500001];
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n;
for (int i = 1; i <= n; ++i) cin >> a[i].first >> a[i].second;
sort(a + 1, a + n + 1);
for (int i = 1; i <= n; ++i)
pre1[i] = pre1[i - 1] + a[i].second;
for (int i = 0; i < n - 1; ++i)
pre2[i] = pre1[i] - a[i + 1].first;
long long res = -1e18, mn = pre2[0];
for (int i = 1; i <= n; ++i){
res = max(res, pre1[i] - a[i].first - mn);
mn = min(mn, pre2[i]);
}
cout << res;
}
