#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main()
{
ll n;
cin>>n;
vector<pair<ll,ll>> a(n);
for(ll i = 0;i < n;i++)cin>>a[i].first>>a[i].second;
sort(a.begin(),a.end());
a.push_back({1e15+1,0});
vector<pair<ll,ll>> v;
for(ll i = 0;i < n;i++)
{
if(a[i].first == a[i+1].first)a[i+1].second += a[i].second;
else v.push_back(a[i]);
}
n = v.size();
vector<pair<ll,ll>> p(n);
p[0] = {v[0].second,0ll};
for(ll i = 1;i < n;i++)p[i] = {p[i-1].first + v[i].second - (v[i].first - v[i-1].first),i};
sort(p.begin(),p.end(),greater<pair<ll,ll>>());
ll j = 0,i = 0,ans = 0,k = 0;
while(i < n)
{
ll mx,pos;
while(p[j].second < i)j++;
mx = p[j].first;pos = p[j].second;
ans = max(ans,mx+k);
for(i = i+1;i <= pos;i++)
{
k += v[i].first - v[i-1].first - v[i-1].second;
ans = max(ans,mx+k);
}
k += v[i].first - v[i-1].first - v[i-1].second;
}
cout<<ans;
return 0;
}
