#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define pb push_back
#define ii pair<int, int>
#define sz(v) (int)v.size()
#define all(v) v.begin(), v.end()
using namespace std;
const int N=1e5+5, mod = 1e9+7, inf = 1e18;
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n; cin >> n;
ii a[n+1]; for (int i=1; i<=n; i++) cin >> a[i].fi >> a[i].se;
sort(a+1, a+n+1);
int p[n+1]; p[0] = 0; for (int i=1; i<=n; i++) p[i] = p[i-1] + a[i].se;
int mx = -inf;
int ans = -inf;
for (int i=n; i>=1; i--) {
mx = max(mx, p[i]-a[i].fi);
ans = max(ans, mx-p[i-1]+a[i].fi);
}
cout << ans;
}
