//I love ManchesterUnited
#include<bits/stdc++.h>
using namespace std;
#define love ManchesterUnited
#define int long long
#define pb push_back
#define FOR(i,a,b) for (int i=(a); i<=(b); i++)
#define FORD(i,b,a) for (int i=(b); i>=(a); i--)
#define endl '\n'
typedef long long ll;
const int N = 5e5 + 5;
const int INF = 1e18;
int n;
pair<int,int> a[N];
int P[N];
int32_t main(){
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> n;
FOR(i,1,n) cin >> a[i].first >> a[i].second;
sort(a+1, a+n+1);
FOR(i,1,n) P[i] = P[i-1] + a[i].second;
int ans = -INF;
int minPref = INF;
FOR(i,1,n){
if (i >= 2) ans = max(ans, (P[i] - a[i].first) - minPref);
minPref = min(minPref, P[i-1] - a[i].first);
}
cout << ans << endl;
}
