#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
const int MAXN = 3e5 + 10;
const int MOD = 1e9 + 7;
#define int long long
int rnd(int x, int y) { // random number generator
int u= uniform_int_distribution<int>(x, y)(rng); return u;
}
void solve(int tc) {
int N;
cin >> N;
pair<int, int> p[N+1];
for(int i=1; i<=N; i++) cin >> p[i].first >> p[i].second;
sort(p+1, p+N+1);
int ps[N+1] = {};
for(int i=1; i<=N; i++) ps[i] = ps[i-1] + p[i].second;
pair<int, int> mx[N+2];
mx[N+1] = {-1e16, N + 1};
for(int i=N; i>=1; i--) {
mx[i] = max(mx[i+1], {ps[i] - p[i].first, i});
}
int ans = 0;
for(int i=1; i<=N; i++) ans = max(ans, mx[i].first - ps[i-1] + p[i].first);
cout << ans << "\n";
}
int32_t main(){
ios::sync_with_stdio(0); cin.tie(0);
int t = 1; //cin >> t;
for(int i=1; i<=t; i++) solve(i);
}
