#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) begin(x), end(x)
#define inf (int)3e18
#define ff first
#define ss second
#define mem(x, y) fill(begin(x), end(x), y)
using vi = vector<int>;
using vpii = vector<pair<int, int>>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
const int MAX = 5e5 + 5;
pii a[MAX];
int pref[MAX];
void solve()
{
int n;
cin>>n;
for(int i = 1;i<=n;i++)
cin>>a[i].ff, cin>>a[i].ss;
sort(a + 1, a + n+ 1);
for(int i = 1;i<=n;i++)
pref[i] = pref[i - 1] + a[i].ss;
int mx = 0;
for(int l = 1;l<=n;l++)
{
for(int r = l+1;r<=n;r++)
{
int sum = pref[r] - pref[l - 1] - a[r].ff + a[l].ff;
mx=max(mx, sum);
}
}
cout<<mx;
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int tt = 1;
// cin >> tt;
while (tt--)
solve();
}
