#include<bits/stdc++.h>
using namespace std;
#define mp make_pair
#define INF 10000000
#define MOD 1000000007
#define ll long long
#define F first
#define S second
typedef pair<ll, ll> ii;
typedef pair<ii, ll> iii;
typedef vector<ll> vi;
typedef vector<ii> vii;
typedef map<ll, ll> mii;
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
ll n;
cin>>n;
vii v(n+1);
for(ll i=1;i<=n;i++){
cin>>v[i].F>>v[i].S;
}
sort(v.begin(), v.end());
ll pref[n+1];
pref[0] = 0;
for(ll i=1;i<=n;i++){
pref[i] = pref[i-1] +v[i].S;
}
ll maxd[n+1];
maxd[n] = pref[n] - v[n].F;
for(ll i=n-1;i>=0;i--){
maxd[i] = max(maxd[i+1], pref[i]-v[i].F);
}
ll maxans = 0;
for(ll i=1;i<=n;i++){
maxans = max(maxans, v[i].F-pref[i-1] + maxd[i]);
}
cout<<maxans<<endl;
}
