#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;
long long n,max1=0,tong=0;
vector<long long> v;
pair<long long,long long> p[500005];
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> n;
for(int i=1;i<=n;i++) cin >> p[i].fi >> p[i].se;
sort(p+1,p+n+1);
v.push_back(p[1].se);
for(int i=2;i<=n;i++)
{
v.push_back(p[i-1].fi - p[i].fi);
v.push_back(p[i].se);
}
for(int i=0;i<v.size();i++)
{
tong += v[i];
if(tong < 0) tong = 0;
max1 = max(max1,tong);
}
cout << max1;
}
