// https://oj.uz/problem/view/JOI18_stove
// OI\JOI18\JOI18-art.pdf
#include <bits/stdc++.h>
using namespace std;
// Macros
#define pb push_back
#define pf push_front
#define ff first
#define ss second
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
// #define rep(i, x, n) for(int i = x; i < n; ++i)
// #define rrep(i, x, n) for(int i = x; i >= n; --i)
// Read and Print
#define read(a, n) for(ll i = 0; i < n; ++i) cin >> a[i];
#define print(a, n) for(ll i = 0; i < n; ++i){ cout << a[i] << " ";} cout << "\n";
#define endl "\n"
#define sp " "
// Typedefs
typedef long long ll;
typedef long double ld;
typedef pair <ll, ll> pii;
typedef vector <ll> vi;
typedef vector <vector <ll>> vvi;
using vec = vector<int>;
// Constants
const ll mxn = 1e6 + 5;
const ll mod = 1e9 + 7;
// Solve
void solve() {
int n; cin>>n;
vector<pii> a(n+1);
for(int i = 0; i<n; i++){
cin>>a[i].ff>>a[i].ss;
}
sort(all(a));
ll ans = 0;
vi sum(n+1, 0), mx(n+1, 0);
// sum[0]=0;
// mx[0]=0;
for(int i = 1; i<=n; i++){
sum[i]=sum[i-1]+a[i].ss;
mx[i]=max(mx[i-1], a[i].ff-sum[i-1]);
ans = max(ans, sum[i]-a[i].ff+mx[i]);
}
cout<<ans<<endl;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
solve();
return 0;
}
