#include <bits/stdc++.h>
using namespace std;
#define int long long
#define OYY LLONG_MAX
#define faster ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define fi first
#define se second
#define FOR for(int i=1;i<=n;i++)
#define mid (start+end)/2
#define pb push_back
#define lim 5005
typedef long long lo;
int n;
int dizi[lim][2];
int pre[lim];
vector<pair<int,int>> v;
int32_t main(){
faster
cin>>n;
FOR{
cin>>dizi[i][0]>>dizi[i][1];
v.pb({dizi[i][0],dizi[i][1]});
}
sort(v.begin(),v.end());
for(int i=0;i<n;i++){
dizi[i+1][0]=v[i].fi;
dizi[i+1][1]=v[i].se;
}
FOR{
pre[i]=pre[i-1]+dizi[i][1];
}
int cev=-LLONG_MAX;
FOR{
for(int j=i;j<=n;j++){
cev=max(cev,pre[j]-pre[i-1]-(dizi[j][0]-dizi[i][0]));
}
}
cout<<cev<<'\n';
return 0;
}
