#include<bits/stdc++.h>
using namespace std;
#define int long long int
#define pii pair<int,int>
#define vi vector<int>
#define si set<int>
#define pb push_back
void solve() {
int n; cin>>n;
pii v[n+1];
for (int i=1;i<=n;i++) {
cin>>v[i].first>>v[i].second;
}
sort(v+1, v+n+1);
int ans = 0;
int sum[n+1];
for(int i = 1; i <= n; ++i) {
sum[i] = sum[i - 1] + v[i].second;
ans = max(ans, 1ll * v[i].second);
}
priority_queue<int, vector<int>, greater<int>> pq;
for(int i = 1; i <= n; ++i) {
if(!pq.empty()) {
int top = pq.top();
ans = max(ans, sum[i] - v[i].first - top);
}
pq.push(sum[i - 1] - v[i].first);
}
cout << ans;
return;
}
int32_t main() {
ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
int tt=1; //cin>>tt;
while(tt--) {
solve();
}
return 0;
}
