#include <bits/stdc++.h>
#define int long long
using namespace std;
typedef pair<int,int> pii;
signed main() {
int n; cin>>n;
vector<pii> a(n);
for(int i=0;i<n;i++) {
int s,v; cin>>s>>v;
a[i] = {s,v};
}
sort(a.begin(),a.end());
vector<int> p(n+1);
p[0]=0;
for(int i=1;i<=n;i++) {
p[i] = p[i-1] + a[i-1].second;
}
//for(int i=0;i<=n;i++) cout<<p[i]<<" ";
//cout<<"\n";
vector<int> mx(n);
int cur=LLONG_MIN;
for(int i=n-1;i>=0;i--) {
cur = max(cur, p[i+1]-a[i].first);
mx[i] = cur;
}
//for(int i=0;i<n;i++) cout<<mx[i]<<" ";
//cout<<"\n";
int ans=LLONG_MIN;
for(int i=0;i<n;i++) {
ans = max(ans, a[i].first-p[i]+mx[i]);
}
cout<<ans;
}
