#include<bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define ii pair<ll,ll>
#define iii pair<ii,ll>
#define pb push_back
using namespace std;
const ll N=5e5+9;
const ll mod=1e9+7;
const ll S=320;
ii a[N];
ll b[N],i,ma,n;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
cin>>n;
for(i=1;i<=n;i++)
cin>>a[i].fi>>a[i].se;
sort(a+1,a+n+1);
// using i
for(i=1;i<n;i++)
b[i]=a[i].se+a[i].fi-a[i+1].fi;
ll res=a[1].se;
ma=max(0ll,b[1]);
for(i=2;i<=n;i++)
{
res=max(res,a[i].se+ma);
ma=max(0ll,ma+b[i]);
}
cout<<res;
}
/*
3
2 3
11 2
4 5
2 4 11
3 5 2
*/
