// Programmer: Shadow1
#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using str = string; // yay python!
#define i64 int64_t
#define show(x) cerr << (#x) << " = " << (x) << '\n';
#define output_vector(v) for(auto &x : v){cout << x << ' ';}cout << '\n';
#define output_pairvector(v) for(auto &x : v){cout << x.first << " " << x.second << '\n';}
#define read_vector(v) for(auto &x : v){cin >> x;}
#define vt vector
#define prq priority_queue
#define pb push_back
#define eb emplace_back
#define pii pair<int,int>
#define fir first
#define sec second
#define sz(x) ll(x.size())
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define int long long
#define discretize(x) sort(x.begin(), x.end()); x.erase(unique(x.begin(), x.end()), x.end());
//
const int INF = 1e15;
void solve() {
int n;
cin >> n;
vector<pii> a(n+1);
for(int i=1; i<=n; ++i)
cin >> a[i].fir >> a[i].sec;
sort(all(a));
vector<int> ps(n+1);
for(int i=1; i<=n; ++i) {
ps[i] = ps[i-1] + a[i].sec;
}
int maxx = -INF, ans = -INF;
for(int i=0; i<=n; ++i) {
maxx = max(maxx, a[i].fir - ps[i-1]);
ans = max(ans, ps[i] - a[i].fir + maxx);
}
cout << ans << '\n';
}
// CHECK YOUR OVERFLOWS!!!!
signed main() {
// freopen("output.txt", "w", stdout);
// freopen("input.txt", "r", stdin);
ios::sync_with_stdio(false);
cin.tie(NULL);
int T = 1;
// cin >> T;
for(int tc = 1; tc <= T; ++tc) {
// cout << "Case #" << tc << ": ";
solve();
}
return 0;
}
