#include<bits/stdc++.h>
#define TASKNAME "codeforce"
#define pb push_back
#define pli pair<int,int>
#define fi first
#define se second
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL);
using namespace std;
using ll=long long;
const ll maxN=5e5+10;
const ll inf=1e18;
const ll mod=1e9+7;
#define int ll
ll a[maxN],pre[maxN],b[maxN],n,ans=-inf;
void solve()
{
vector<pli>vec;
cin >> n;
for(int i=1;i<=n;i++) cin >> a[i] >> b[i],vec.pb({a[i],b[i]});
sort(vec.begin(),vec.end());
for(int i=1;i<=n;i++)
{
a[i]=vec[i-1].fi;
b[i]=vec[i-1].se;
}
ll mn=inf;
for(int i=1;i<=n;i++)
{
pre[i]=pre[i-1]+b[i];
mn=min(mn,pre[i-1]-a[i]);
ans=max(ans,pre[i]-a[i]-mn);
}
cout << ans;
}
signed main()
{
fastio
//freopen(TASKNAME".INP","r",stdin);
//freopen(TASKNAME".OUT","w",stdout);
solve();
}
