#include <bits/stdc++.h>
#define int long long
using namespace std;
const int NMAX=5e5, INF=1e9*1ll*1e9;
int sz[NMAX+1], val[NMAX+1], sp[NMAX+1];
struct obiect
{
int s, v;
const bool operator < (const obiect &o) const{
return s<o.s;
}
}o[NMAX+1];
signed main()
{
int n;
cin>>n;
for(int i=1; i<=n; i++)
cin>>o[i].s>>o[i].v;
sort(o+1, o+n+1);
for(int i=1; i<=n; i++)
{
sz[i]=o[i].s;
val[i]=o[i].v;
sp[i]=sp[i-1]+val[i];
}
int best=-INF;
int ans=0;
for(int i=1; i<=n; i++)
{
best=max(best, sz[i]-sp[i-1]);
ans=max(ans, sp[i]-sz[i]+best);
}
cout<<ans;
return 0;
}
