/// Template path: /home/mohammed/.config/sublime-text-3/Packages/User
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
// typedef
typedef long long ll;
typedef long double ld;
typedef vector<int> vecint;
typedef vector<char> vecchar;
typedef vector<string> vecstr;
typedef vector<long long> vecll;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
// Marcos
#define endl ("\n")
#define int long long
#define mod 1000000007
#define pi (3.141592653589)
#define REP(i,a,b) for (int i = a; i < b; i++)
#define RREP(i,a,b) for (int i = a; i > b; i--)
#define fast ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr)
// Functions
long long squared(long long x) {return (x * x) % mod;}
int factorial(int n) {long long res = 1; for (int i = 1; i <= n; i++) {res = ((res * i) % mod + mod) % mod ;} return res;}
long long power(long long x, long long p) {if (p == 0) {return 1;} if (p % 2 == 1) {return (power(x, p - 1) * x) % mod;} return squared(power(x, p / 2));}
// cout << fixed;
// cout << setprecision(4);
// ---------(^_^)--------- //
void main_solve() {
int n; cin >> n;
vector<vector<int>> v;
for (int i = 0 ; i < n; i ++) {
int a, b; cin >> a >> b;
v.push_back({a, b});
}
sort(v.begin(), v.end());
vector<int> pre;
pre.push_back(0);
for (int i = 0 ; i < n; i ++) {
pre.push_back(pre[i] + v[i][1]);
}
multiset<int> s;
for (int i = n - 1; i >= 0; i --) {
s.insert(pre[n] - pre[i] + v[i][0]);
}
int result = 0;
for (int i = n - 1; i >= 0; i --) {
auto it = s.end();
it--;
int e = (*it - (pre[n] - pre[i + 1])) - v[i][0];
result = max(e, result);
s.erase(s.lower_bound(pre[n] - pre[i] + v[i][0]));
}
cout << result << endl;
}
int32_t main() {
fast;
// #ifndef ONLINE_JUDGE
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
// #endif
// Just another problem (-_-)
int t;
t = 1;
// cin >> t;
while (t--) {
main_solve();
}
}
