#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define ff first
#define ss second
#define vl vector<long long>
#define vi vector<int>
#define pii pair<int,int>
#define pll pair<long long, long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace std;
//mt19937 mt;void random(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll rand(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
//random();
int n;
cin >> n;
vector<pll> v;
rep(i,n)
{
ll a,b;
cin >> a >> b;
v.pb({a,b});
}
sort(all(v));
ll ans = -1e18;
ll val = -1e18;
ll pref = 0;
rep(i,n)
{
val = max(val,-v[i].ff-pref);
pref += v[i].ss;
ans = max(ans,val+pref+v[i].ff);
}
cout << ans << "\n";
}
