#include <bits/stdc++.h>
#define FOR(i, begin, end) for(int i=(begin); i<(end); i++)
#define pb push_back
using namespace std;
typedef vector<int> vi;
typedef long long ll;
const int N=5e3+10;
int n;
vi in;
ll a[N], b[N], p[N];
bool cmp(int i, int j)
{
return a[i]<=a[j];
}
int main()
{
cin >> n;
FOR(i, 0, n)
{
cin >> a[i] >> b[i];
in.pb(i);
}
sort(in.begin(), in.end(), cmp);
FOR(k, 0, n)
{
int i=in[k];
p[k+1]=p[k]+b[i];
}
ll ans=0;
FOR(k, 0, n)
{
int i=in[k];
//cout << a[i] << " " << b[i] << endl;
FOR(b, k, n)
{
int j=in[b];
ll sum=p[b+1]-p[k];
//cout << k << " " << b << " " << sum << endl;
ans=max(ans, sum-a[j]+a[i]);
}
}
cout << ans;
}
