#include <bits/stdc++.h>
using namespace std;
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#pragma GCC optimize("Ofast,unroll-loops,fast-math,O3")
#define pb push_back
#define ll long long
#define int long long
//#define sort(all(v)) sort(v.begin(),v.end())
int mod = 998244353;
const int N = 4e5 + 10;
const int inf = 1e9;
int fact[200001];
ll binpow(ll a, ll b){
if(b == 0) return 1;
else if(b % 2 == 1) return (a * binpow(a, b - 1)) % mod;
ll p = binpow(a,b / 2);
return (p * p) % mod;
}
int p[N];
signed main(){
//freopen("mootube.in", "r", stdin);
//freopen("mootube.out", "w", stdout);
int n;
cin >> n;
vector <pair<int,int>> v;
v.pb({1,1});
for(int i = 1; i <= n; i++){
int a,b;
cin >> a >> b;
v.pb({a,b});
}
sort(v.begin(),v.end());
vector <int> pr(n + 1);
int ans = 0;
for(int i = 1;i <= n; i++){
pr[i] = pr[i - 1] + v[i].second;
}
multiset <int> mt;
for(int i = 1; i <= n; i++){
if(mt.size() > 0)ans = max(ans,pr[i] - v[i].first + *mt.rbegin());
ans = max(ans,pr[i] - pr[i - 1]);
mt.insert(v[i].first - pr[i - 1]);
}
cout << ans;
}
