#include <iostream>
#include <vector>
#include <algorithm>
#define ll long long
#define X first
#define Y second
#define endl '\n'
using namespace std;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
}
int n;
const int MAXN = 500100;
pair<ll, ll> a[MAXN];
vector<pair<ll, ll>> b;
ll mx = 0;
vector<ll> pref;
void read()
{
mx = 0;
cin >> n;
for (int i = 1; i <= n; i++)
{
cin >> a[i].X >> a[i].Y;
mx = max(mx, a[i].Y);
}
sort(a + 1, a + 1 + n);
b.push_back({0, 0});
for (int i = 1; i <= n; i++)
{
if (b.back().X == a[i].X)
b.back().Y += a[i].Y;
else
b.push_back(a[i]);
}
pref.push_back(0);
for (int i = 1; i < b.size(); i++)
{
//cout << b[i].X << ' ' << b[i].Y << endl;
pref.push_back( pref[i - 1] + b[i].Y);
}
}
void solve()
{
for (int l = 1; l < b.size(); l++)
for (int r = l; r < b.size(); r++)
{
mx = max(mx, (pref[r] - pref[l - 1]) - (b[r].X - b[l].X));
}
}
signed main()
{
speed();
read();
solve();
cout << mx << endl;
return 0;
}
