/*
#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")
#pragma GCC optimize("unroll-loops")
*/
#include <bits/stdc++.h>
#define taskname "bai3"
#define all(x) x.begin(), x.end()
#define ll long long
#define ull unsigned ll
#define ld long double
#define pb push_back
#define ff first
#define ss second
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
using namespace std;
using cd = complex<double>;
const int mxN = 2e5 + 5;
const int mod = 1e9 + 7;
const ll oo = 1e18;
int n;
pll p[mxN];
void solve() {
cin >> n;
for(int i = 1; i <= n; ++i) {
cin >> p[i].ff >> p[i].ss;
}
sort(p + 1, p + n + 1);
ll ans = p[1].ss, maxx = p[1].ff, pre = p[1].ss;
for(int i = 2; i <= n; ++i) {
maxx = max(maxx, p[i].ff - pre);
pre += p[i].ss;
ll tmp = pre - p[i].ff + maxx;
ans = max(ans, tmp);
}
cout << ans << "\n";
}
signed main() {
#ifdef CDuongg
freopen("bai3.inp", "r", stdin);
freopen("bai3.out", "w", stdout);
auto start = chrono::high_resolution_clock::now();
#endif
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int t = 1; //cin >> t;1
while(t--) solve();
#ifdef CDuongg
auto end = chrono::high_resolution_clock::now();
cout << "\n"; for(int i = 1; i <= 100; ++i) cout << '=';
cout << "\nExecution time: " << chrono::duration_cast<chrono::milliseconds> (end - start).count() << "[ms]" << endl;
#endif
}
