#include <bits/stdc++.h>
#define int long long
using namespace std;
int a;
pair<int,int> z[1000005];
int f[4000005];
int max1=0;
int curmax=0;
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> a;
for (int i=1;i<=a;i++){
cin >> z[i].first >> z[i].second ;
}
sort(z+1,z+1+a);
for (int i=1;i<=a;i++){
int p=curmax;
int preval=p+z[i].second-z[i].first;
preval=max(preval,z[i].second);
max1=max(max1,preval);
curmax=max(curmax+z[i].second,z[i].second+z[i].first);
}
cout << max1 << "\n";
return 0;
}
