/*
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*/
#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ll long long
#define ull unsigned long long
#define ld long double
#define str string
#define ch char
#define db double
#define pb push_back
#define ff first
#define ss second
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define YES cout<<"YES\n";
#define NO cout<<"NO\n";
#define Bob cout<<"Bob\n";
#define Alice cout<<"Alice\n";
#define ordered_set tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update>
const ll INF = 1000000000000000000;
void solve(){
ll n;
cin>>n;
vector<pair<ll,ll>>v(n);
for(int i = 0;i<n;i++){
cin>>v[i].ff>>v[i].ss;
}
sort(all(v));
ll mx=0;
ll sum=0;
ll kh = -INF;
for(int i = 0;i<n;i++){
ll alma = v[i].ff;
ll armud = v[i].ss;
kh = max(kh,alma-sum);
sum+=armud;
mx=max(mx,sum-alma+kh);
}
cout<<mx;
}
signed main(){
ll t = 1;
//cin>>t;
while(t--){
solve();
}
return 0;
}
