#include <bits/stdc++.h>
#include <iostream>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update> order_set;
mt19937 mt_rand(chrono::high_resolution_clock::now().time_since_epoch().count());
//uniform_int_distribution<int> gen(-1e9, 1e8); ///(min, max)
//int random() {return gen(mt_rand);}
const int mxN = 1e6+50000;
const int mod = 998244353;
const int mxlogN = 34;
const int mxK = 26;
const ll inf = 1e18;
const int K = 100000;
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int n; cin >> n;
vector<pair<ll, int>> a(n);
for(int i=0; i<n; i++) cin >> a[i].first >> a[i].second;
sort(a.begin(), a.end());
ll ans=-inf, mx=-inf;
for(int i=0; i<n; i++)
{
if(i) mx-=a[i].first-a[i-1].first;
mx=max(mx,0LL);
mx+=a[i].second;
ans=max(ans,mx);
}
cout << ans << "\n";
}
