#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define OPT ios_base::sync_with_stdio(0); \
cin.tie(0); \
cout.tie(0)
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pull pair<ull,ull>
#define endl "\n"
#define all(v) v.begin(), v.end()
#define mpr make_pair
#define pb push_back
#define ts to_string
#define fi first
#define se second
#define inf 0x3F3F3F3F
#define bpc __builtin_popcount
#define print(v) for(int i = 0; i < v.size(); i++) \
cout << v[i] << " "; \
cout<<endl;
int main()
{
int n;
cin >> n;
vector<pll> v(n);
ll res = 0;
for (int i = 0; i < n; i++)
{
cin >> v[i].fi >> v[i].se;
res = max(res, v[i].se);
}
sort(all(v));
ll sum = 0;
vector<ll> rest(n);
for (int i = 0; i < n; i++)
{
if (v[i].fi >= sum) sum = v[i].fi;
sum += v[i].se;
rest[i] = sum;
}
for (int i = 0; i < n; i++)
{
res = max(res, rest[i] - v[i].fi);
}
cout << res << endl;
}
