#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define f first
#define s second
#define mp make_pair
#define pb push_back
#define vll vector<ll>
#define pll pair<ll,ll>
using namespace std;
const ll N = 5e5+100;
const ll MOD = 1e9+7;
ll pre[N];
ll maxx[N];
int main()
{
ll n;
cin>>n;
pll a[n+1];
for(int i =1;i<=n;i++)cin>>a[i].f >> a[i].s;
sort(a+1,a+n+1);
for(int i =1;i<=n;i++){
pre[i] = pre[i-1] + a[i].s;
}
for(int i =1;i<=n;i++){
maxx[i] = max(maxx[i-1],a[i].f-pre[i-1]);
}
ll ans = 0;
for(int j =1;j<=n;j++){
ans = max(ans,(pre[j]-a[j].f) + (maxx[j]));
}
cout<<ans<<endl;
return 0;
}
