#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
#define endl '\n'
#define pb push_back
#define ff first
#define ss second
#define all(a) a.begin(),a.end()
#define gcd(a,b) __gcd(a,b)
#define lcm(a,b) (a*(b/gcd(a,b)))
#define fios(); ios_base::sync_with_stdio(0);cin.tie(0);
#define file(); freopen("input.txt","r",stdin);freopen("output.txt","w",stdout);
void solve(){
int n; cin>>n;
vector<pair<int,int>> v(n+1,{0,0});
for(int i=1;i<=n;i++){
int x,y; cin>>x>>y;
v[i]={x,y};
}
sort(all(v));
//for(int i=1;i<=n;i++) cout<<v[i].ff<<' '; cout<<endl;
//for(int i=1;i<=n;i++) cout<<v[i].ss<<' '; cout<<endl;
int pre[n+1]={0};
int c[n+1]={0};
for(int i=1;i<=n;i++){
pre[i]=pre[i-1]+v[i].ss;
c[i]=pre[i]-v[i].ff;
}
int sufmx[n+1]={0};
int mx=-1e16;
for(int i=n;i>0;i--){
mx=max(mx,c[i]);
sufmx[i]=mx;
}
int ans=-1;
for(int i=1;i<=n;i++){
int x=v[i].ff-pre[i-1];
ans=max(ans,x+sufmx[i]);
}
cout<<ans<<endl;
return;
}
int32_t main(){
fios();
solve();
return 0;
}
