#include <bits/stdc++.h>
#define ll long long
#define MAXN 500010
using namespace std;
pair<ll,ll> a[MAXN];
bool Cmp(pair<ll,ll> x,pair<ll,ll> y)
{
if (x.first!=y.first)
return x.first<y.first;
return x.second<y.second;
}
int main()
{
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
ll n;
cin >> n;
for (ll i=1;i<=n;i++)
cin >> a[i].first >> a[i].second;
sort(a+1,a+1+n);
ll ans=LLONG_MIN,sum=0,minn=LLONG_MAX;
for (ll i=1;i<=n;i++)
{
minn=min(minn,sum-a[i].first);
sum+=a[i].second;
ans=max(ans,sum-a[i].first-minn);
}
cout << ans;
return 0;
}
