#include <bits/stdc++.h>
#define int long long
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define sc second
#define endl "\n"
#define pii pair<int,int>
using namespace std;
const int MAXN = 1e5+5;
const int mod7 = 1e9+7;
const long long inf = 1e18;
signed main()
{
ios_base::sync_with_stdio(false),cin.tie(0), cout.tie(0);
int tt=1;
//cin >> tt;
while(tt--)
{
int n;
cin >> n;
vector<pii> niz(n);
for(int i=0; i<n; i++)cin >> niz[i].fi >> niz[i].sc;
sort(all(niz));
int mx = 0;
int rez = 0;
vector<int> pref(n+1);
for(int i=1; i<n+1; i++) pref[i] = pref[i-1] + niz[i-1].sc;
for(int i=0; i<n; i++)
{
mx = max(mx, -pref[i] + niz[i].fi);
rez = max(rez,pref[i+1] + mx - niz[i].fi);
}
cout << rez << endl;
}
}
