#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define int long long
#define sz(a) (int)a.size()
#define all(a) a.begin(),a.end()
const int mxN = (int)5e5+10;
int n, m, a[mxN];
pair<int,int> v[mxN];
int32_t main() {
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> n; int ans = 0;
for(int i = 0; i < n; i++)
cin >> v[i].fi >> v[i].se, ans = max(ans, v[i].se);
sort(v,v+n); int sum = 0, mx = 0;
for(int i = 0; i < n; i++){
sum+=v[i].se;
ans = max(ans, sum-v[i].fi+mx);
mx = max(mx,v[i].se+v[i].fi-sum);
}
cout << ans;
}
