#include <bits/stdc++.h>
#define taskname ""
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define for0(i, n) for (int i = 0; i < (int)(n); ++i)
#define for1(i, n) for (int i = 1; i <= (int)(n); ++i)
#define ford(i, n) for (int i = (int)(n) - 1; i >= 0; --i)
#define fore(i, a, b) for (int i = (int)(a); i <= (int)(b); ++i)
using namespace std;
typedef long long ll;
typedef long double ld;
typedef complex <ld> cd;
typedef vector <cd> vcd;
typedef vector <int> vi;
template<class T> using v2d = vector <vector <T> >;
template<class T> bool uin(T &a, T b)
{
return a > b ? (a = b, true) : false;
}
template<class T> bool uax(T &a, T b)
{
return a < b ? (a = b, true) : false;
}
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
const int maxN = 5e5 + 10;
int n;
struct pic
{
ll a, b;
pic() {}
pic(ll a, ll b) : a(a), b(b) {}
} art[maxN];
ll prefix[maxN];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
for1(i, n)
{
cin >> art[i].a >> art[i].b;
}
sort(art + 1, art + n + 1, [](pic x, pic y)
{
return x.a < y.a;
});
ll res = 0;
for1(i, n)
{
//set with 1 elements
uax(res, art[i].b);
}
for1(i, n)
{
prefix[i] = prefix[i - 1] + art[i].b;
}
ll kmax = prefix[n] - art[n].a;
for (int i = n - 1; i; --i)
{
uax(res, kmax - prefix[i] + art[i].a + art[i].b);
uax(kmax, prefix[i] - art[i].a);
}
cout << res;
return 0;
}
