#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
const int N = 5e5+5 ;
const int M = 1e7+5;
const int mod = 1e9+7;
pair<int,int> a[N] ;
int sufmax[N] ;
int ps[N] ;
signed main(){
ios_base::sync_with_stdio(false) ;
cin.tie(0) ; cout.tie(0) ;
int n ;
cin >> n ;
for (int i = 1 ; i<= n ;i++) {
cin >> a[i].first >> a[i].second ;
}
sort(a+1, a+1+n);
for (int i = 1; i<= n ;i++) {
ps[i] = ps[i-1] + a[i].second ;
}
sufmax[n+1] = -1e18 ;
for (int i = n ;i >= 1 ;i--) {
sufmax[i] = max(sufmax[i+1] , ps[i] - a[i].first) ;
}
int mn = LLONG_MAX ;
int res= 0 ;
for (int i = 0 ; i < n ;i++) {
mn = min(mn ,ps[i] - a[i+1].first) ;
//cout << mn << " " << sufmax[i+1] << endl ;
res = max(res, sufmax[i+1] - mn) ;
}
cout << res ;
}
