#include <stdio.h>
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <random>
#include <chrono>
#include <queue>
#include <functional>
#include <iostream>
#include <queue>
//#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define ld long double
const ll maxn = 1e6 + 1, maxm = 1e7 + 1;
const ll mod = 1e9 + 7, mod2 = 998244353, inf = 1e9, block = 550, hb = 31, base = 1000050017;
const ld eps = 1e-9;
ll n;
ll a[maxn], b[maxn], pref[maxn];
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n;
for (int i = 1; i <= n; ++i){
cin >> a[i] >> b[i];
}
vector<pair<ll, ll>> vec;
for (int i = 1; i <= n; ++i){
vec.pb(mp(a[i], b[i]));
}
sort(vec.begin(), vec.end());
for (int i = 0; i < n; ++i){
pref[i] = (i - 1 >= 0 ? pref[i - 1] : 0) + vec[i].s;
}
ll mx = -inf * inf, ans = -inf * inf;
for (int i = n - 1; i >= 0; --i){
//cout << vec[i].f << " " << vec[i].s << '\n';
mx = max(mx, pref[i] - vec[i].f);
ans = max(ans, mx - (i - 1 >= 0 ? pref[i - 1] : 0) + vec[i].f);
}
cout << ans;
}
