#include <bits/stdc++.h>
#define speed ios_base::sync_with_stdio(0); cin.tie(0)
#define all(x) x.begin(), x.end()
#define F first
#define S second
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
const ll oo=0x3f3f3f3f3f3f3f3f;
int main() {
speed;
int n;
cin>>n;
vector<pll> pr(n+1);
for (int i=1;i<=n;i++) {
cin>>pr[i].F>>pr[i].S;
}
sort(pr.begin()+1,pr.end());
vector<ll> pre(n+1);
for (int i=1;i<=n;i++) pre[i]=pre[i-1]+pr[i].S;
ll ans=-oo;
ll mx=-oo;
for (int i=1;i<=n;i++) {
mx=max(pr[i].F-pre[i-1],mx);
ans=max(ans,pre[i]-pr[i].F+mx);;
}
cout<<ans<<"\n";
return 0;
}
