//Dost SEFEROĞLU
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int,int>
#define ff first
#define ss second
#define sp << " " <<
#define all(cont) cont.begin(),cont.end()
#define vi vector<int>
const int MOD = 1e9+7,inf = 2e18;
const int N = 1e5+50;
void solve() {
int n;
cin >> n;
vector<pii> ps(n+1);
for (int i=1;i<=n;i++) cin >> ps[i].ff >> ps[i].ss;
sort(ps.begin()+1,ps.end());
int ans = 0;
vi p(n+1,0);
for (int i=1;i<=n;i++) p[i] = p[i-1]+ps[i].ss;
int mx = -inf;
for (int i=n;i>=1;i--) {
mx = max(mx,p[i]-ps[i].ff);
ans = max(ans,ps[i].ff-p[i-1]+mx);
}
cout << ans << endl;
}
signed main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#ifdef Dodi
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
