#include<bits/stdc++.h>
#define int long long
using namespace std;
int n;
vector<pair<int,int> > n1;
signed main(){
cin>>n;
for (int i = 0;i<n;i++){
int a,b;
cin>>a>>b;
n1.push_back(make_pair(a,b));
}
sort(n1.begin(),n1.end());
int ans = 0;
vector<int> pre;
pre.resize(n);
pre[0] = n1[0].second;
for (int i = 1;i<n;i++){
pre[i] = n1[i].second+pre[i-1];
}
for (int i = 0;i<n;i++){
int ans1 = -n1[i].first;
for (int j = 0;j<=i;j++){
int ans2 = ans1;
if (j!=0) ans2 = ans1+n1[j].first+pre[i]-pre[j-1];
else ans2 = ans1+n1[j].first+pre[i];
ans = max(ans,ans2);
}
}
cout<<ans<<"\n";
return 0;
}
