#include <bits/stdc++.h>
#define int long long
#define task "task"
#define fi first
#define se second
using namespace std;
const int ma = 5e5 + 4;
pair<int, int> a[ma];
int n;
struct node
{
int ans, mi, sum;
} st[ma * 4];
void Read()
{
cin >> n;
for (int i = 1; i <= n; i++) cin >> a[i].fi >> a[i].se;
}
node take(node a, node b)
{
if (a.ans == LLONG_MIN) return b;
if (b.ans == LLONG_MIN) return a;
node ans;
ans.sum = a.sum + b.sum;
ans.mi = max(a.mi, b.mi);
ans.ans = max({ans.sum - ans.mi, a.ans, b.ans});
return ans;
}
void build(int id, int l, int r)
{
if (l == r)
{
st[id].ans = a[l].se - a[l].fi;
st[id].mi = a[l].fi;
st[id].sum = a[l].se;
return;
}
int mid = (l + r) / 2;
build(id * 2, l, mid);
build(id * 2 + 1, mid + 1, r);
st[id] = take(st[id * 2], st[id * 2 + 1]);
}
node get(int id, int tl, int tr, int l, int r)
{
if (l > tr || r < tl) return {LLONG_MIN, 0, 0};
if (l <= tl && tr <= r) return st[id];
int mid = (tl + tr) / 2;
node ansl = get(id * 2, tl, mid, l, r);
node ansr = get(id * 2 + 1, mid + 1, tr, l, r);
return take(ansl, ansr);
}
void solve()
{
sort(a + 1, a + 1 + n);
build(1, 1, n);
int res = LLONG_MIN;
for (int i = 1; i <= n; i++)
{
res = max(res, a[i].fi + get(1, 1, n, i, n).ans);
}
cout << res;
}
signed main()
{
if(fopen(task ".INP", "r"))
{
freopen(task ".INP", "r", stdin);
freopen(task ".OUT", "w", stdout);
}
ios_base::sync_with_stdio(false);
cin.tie(NULL);
Read();
solve();
return 0;
}
