#include<bits/stdc++.h>
using namespace std;
#define rc(x) return cout<<x<<endl,0
#define pb push_back
#define dbg(x) cout << #x << '=' << x << '\n';
#define ll long long
#define int ll
#define sz size()
#define x first
#define y second
#define pi pair <int, int>
#define pii pair <int, pi>
#define vi vector <int>
const ll mod = 1e9 + 7;
int n, net[500004];
vector <pi> art;
int mn[500004];
int32_t main(){
ios_base :: sync_with_stdio(0); cin.tie(); cout.tie();
cin>>n;
art.resize(n+1);
for(int i=1; i<=n; i++) cin>>art[i].x>>art[i].y;
art[0]={0, 0};
sort(art.begin(), art.end());
//for(int i=1; i<=n; i++) art[i].x-=art[1].x;
//net[1]=art[1].y;
///cout<<endl;for(int i=1; i<=n; i++) cout<<art[i].x<<" "<<art[i].y<<endl; cout<<endl;
for(int i=1; i<=n; i++) net[i]=art[i].y-(art[i].x-art[i-1].x);
///for(int i=1; i<=n; i++) cout<<net[i]<<" "; cout<<endl;
for(int i=1; i<=n; i++) net[i]+=net[i-1];
///for(int i=1; i<=n; i++) cout<<net[i]<<" "; cout<<endl;
mn[n]=net[n];
for(int i=n-1; i>=1; i--) mn[i]=max(mn[i+1], net[i]);
int ans=0;
for(int i=1; i<=n; i++){
/*if(i==6){
dbg(mn[i]);
dbg(net[i-1]);
dbg(art[i].x);
}*/
ans=max(ans, mn[i]-net[i-1]+art[i].x-art[i-1].x);
///cout<<ans<<" ";
}
cout<<ans;
}
