#include<bits/stdc++.h>
#define F first
#define S second
#define MAX 500005
#define oo 1e18
#define mod 1000000007
#define fast_in ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);cout.setf(ios::fixed);cout.precision(0);
using namespace std;
typedef long long ll;
#define pll pair<ll , ll>
#define vll vector<ll>
#define vvll vector<vll>
#define vpll vector<pll>
ll m,n;
pll a[MAX];
int main(){
fast_in
cin>>n;
for(int i=0;i<n;i++){
cin>>a[i].F>>a[i].S;
}sort(a,a+n);
ll m=0,s=0,r=0;
for(int i=0;i<n;i++){
m=max(m,a[i].F-s);
s+=a[i].S;
r=max(r,s-a[i].F+m);
}
cout<<r;
return 0;
}
