#include <bits/stdc++.h>
#define int long long
#define pb push_back
using namespace std;
const int N=5e5+10;
const int inf=9e18;
const int mod=1e9+7;
pair<int,int>a[N];
signed main() {
ios_base::sync_with_stdio(NULL);
cin.tie(NULL);
int T=1;
// cin>>T;
while(T--) {
int n;
cin>>n;
int ans=0;
for(int i=1;i<=n;i++) {
cin>>a[i].first>>a[i].second;
ans=max(ans,a[i].second);
}
sort(a+1,a+n+1);
int sum=0,mx=0;
for(int i=1;i<=n;i++) {
sum+=a[i].second;
ans=max(ans,sum-a[i].first+mx);
mx=max(mx,a[i].first-sum+a[i].second);
}
cout<<ans<<"\n";
}
}
