#include <bits/stdc++.h>
#define zet ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define pb push_back
#define int long long
#define lvs main
#define pii pair<int, int>
using namespace std;
//const ll NN = 1e18+7;
//const int N = 1e5+15;
//pair<int, int> p[N];
//int a[N], sqr;
signed lvs () {
int n; cin >> n;
pii a[n];
for(int i = 0; i < n; i++)cin >> a[i].first >> a[i].second;
sort(a, a + n);
int mx = a[0].second,cnt = a[0].second;
for(int i = 1; i < n; i++){
cnt += a[i].second;
cnt -= (a[i].first - a[i-1].first);
if(cnt < a[i].second) cnt = a[i].second;
mx = max(mx,cnt);
}
cout<<mx;
}
