#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <queue>
using namespace std;
#define int long long
#define ff first
#define ss second
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
vector <pair <int, int>> v(n);
for (int i = 0;i < n;i++) {
cin >> v[i].ff >> v[i].ss;
}
sort(v.begin(), v.end());
int pref[n + 1] = {0};
pref[0] = v[0].ss;
for (int i = 1; i < n; i++) {
pref[i] = v[i].ss;
pref[i] = max(pref[i], pref[i - 1] + v[i].ss - (v[i].ff - v[i - 1].ff));
}
int ans = 0;
for (int i = 0;i < n;i++) {
ans = max(ans, pref[i]);
}
cout << ans << endl;
return 0;
}
