#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
const bool typetest = 0;
const int N = 5e5 + 5;
const ll Inf = 1e17;
int n;
struct OK
{
ll x, y;
bool operator<(const OK &a) const
{
return x < a.x;
}
} a[N];
void Read()
{
cin >> n;
for (int i = 1; i <= n; ++i)
cin >> a[i].x >> a[i].y;
sort(a + 1, a + n + 1);
}
void Solve()
{
a[0].y = 0;
ll maxn(-Inf);
ll ans(-Inf);
for (int i = 1; i <= n; ++i)
{
a[i].y += a[i - 1].y;
maxn = max(maxn, a[i].x - a[i - 1].y);
ans = max(ans, maxn + a[i].y - a[i].x);
}
cout << ans;
}
int32_t main()
{
//ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t(1);
if (typetest)
cin >> t;
for (int _ = 1; _ <= t; ++_)
{
Read();
Solve();
}
}
