#include <algorithm>
#include <fstream>
#include <vector>
#include <queue>
#include <stack>
#include <iostream>
#include <cmath>
#include <queue>
#include <set>
#include <string>
#include <cstring>
#include <map>
#include <unordered_map>
#include <unordered_set>
#define F first
#define S second
#define PB push_back
using namespace std;
const long long MOD=1e9+7, INF=1e18;
const int INFI=1e9;
typedef long long ll;
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ii> vii;
typedef vector<pair<int, ii>> viii;
typedef vector<vii> vvii;
typedef vector<ll> vll;
typedef vector<vll> vvll;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n; cin>>n;
vll pref(n+1, 0);
vector<pair<ll, ll>> info(n);
for(auto &num:info) cin>>num.F>>num.S;
sort(info.begin(), info.end());
for(int i=1;i<=n;i++) pref[i]+=pref[i-1]+info[i-1].S;
ll ans=0;
priority_queue<ll> pq;
for(int i=0;i<n;i++){
ll start=-pref[i]+info[i].F, end=pref[i+1]-info[i].F;
pq.push(start);
//cout<<start<<" "<<end<<endl;
ans=max(ans, end+pq.top());
}
cout<<ans<<endl;
return 0;
}
