#include <iostream>
#include <vector>
#include <algorithm>
#define ll unsigned 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;
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);
for(int i=1;i<=n;i++)
{
if(b.empty())
{
b.push_back(a[i]);
continue;
}
if(b.back().X==a[i].X)b.back().Y+=a[i].Y;
else b.push_back(a[i]);
}
}
void solve()
{
int l = 0;
ll sum = 0;
for (int r = 0; r < b.size(); r++)
{
sum+=a[r].Y;
while(l<r&&((a[l+1].X-a[l].X)>a[l].Y))
{
sum-=a[l].Y;
l++;
}
mx=max(mx,sum-(a[r].X-a[l].X));
}
}
signed main()
{
speed();
read();
solve();
cout<<mx<<endl;
return 0;
}
