#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define ll long long
#define el "\n"
#define alla(a,n) a+1,a+n+1
#define fi first
#define se second
#define all(v) v.begin(),v.end()
#define fu(i,a,b) for(ll i=a;i<=b;i++)
#define fud(i,a,b) for(ll i=a;i>=b;i--)
const ll MOD=1e9+7 ;//1234567891;
const ll inf=1e18;
const ll base = 311;
const ll N=1e6+5;
const ll N1=1e3+5;
template <class T> bool mini(T &x, T y){return (x > y ? x = y, 1 : 0);}
template <class T> bool maxi(T &x, T y){return (x < y ? x = y, 1 : 0);}
template <class T> void add(T &x, ll y){x += y; if(x >= MOD) x -= MOD;}
template <class T> void sub(T &x, T y){x -= y; if(x < 0) x += MOD;}
/*v*/
int dx[8] = {1, -1, 0, 0, 1, 1, -1, -1},
dy[8] = {0, 0, 1, -1, 1, -1, 1, -1};
void rtn()
{
cerr<<el<<"time: "<<clock()<<"ms"<<el;
exit(0);
}
ll n;
pair<ll,ll> art[N];
namespace sub1
{
bool checksub()
{
return n<=5000;
}
void sol()
{
ll ans=0;
fu(i,1,n)
{
ll S=0;
fu(j,i,n)
{
S+=art[j].se;
maxi(ans,S-art[j].fi+art[i].fi);
}
}
cout<<ans;
}
}
namespace sub2
{
ll pre[N];
void sol()
{
fud(i,n,1) pre[i]=pre[i+1]+art[i].se;
ll mi=inf;
ll ans=0;
fud(i,n,1)
{
mini(mi,pre[i+1]+art[i].fi);
maxi(ans,pre[i]+art[i].fi-mi);
}
cout<<ans;
}
}
signed main(void)
{
#define TASK "art"
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);srand(time(0));
if(fopen(TASK".inp","r"))
{
freopen(TASK".inp" ,"r",stdin) ; freopen(TASK".out" ,"w",stdout);
}
cin>>n;
fu(i,1,n) cin>>art[i].fi>>art[i].se;
sort(alla(art,n));
if(sub1::checksub()) return sub1::sol(),0;
return sub2::sol(),0;
return 0;
}
