#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define el cout << "\n"
#define sz(x) (long long)(x).size()
#define all(x) (x).begin(), (x).end()
#define pii pair<int, int>
using ll = long long;
#define int long long
#define FOR(i, a, b) for (int i = a; i <= b; i++)
const long long mx3 = 6e5 + 1, mod = 1e9 + 7 ;
long long pre[mx3],b[mx3] , BrunoFernandes,n,k,m,q ;
ll dp[mx3] ;
void RubenAmorim()
{
cin >> n ;
vector < pii > a(n) ;
FOR ( i , 0 , n - 1 )
{
cin >> a[i].fi >> a[i].se ;
}
sort ( a.begin() , a.end() ) ;
pre[0] = a[0].se ;
FOR ( i , 1 , n - 1 )
{
pre[i] = pre[i-1] + a[i].se ;
}
ll ans = 0 , mn = a[0].fi ;
FOR ( i , 1 , n )
{
ll tmp = pre[i] - a[i].fi + mn ;
//cout << pre[i] << " " << mn << " " << tmp << "\n" ;
ans = max ( ans ,tmp ) ;
mn = max ( mn , a[i].fi - pre[i-1] ) ;
}
cout << ans ;
}
signed main()
{
//freopen("DEQUY7.INP", "r", stdin);
//freopen("DEQUY7.OUT", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie (0); cout.tie(0);
BrunoFernandes = 1;
//cin >> BrunoFernandes;
while (BrunoFernandes--)
RubenAmorim();
}
