#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define pb push_back
#define pii pair<int, int>
#define pll pair<ll, ll>
#define mll map<ll, ll>
#define fi first
#define se second
ll n, t, ans, sum;
int main() {
fastio;
cin >> n;
vector<pll> v(n);
for (auto &u : v) {
cin >> u.fi >> u.se;
}
sort(v.begin(), v.end());
for (int i = 0; i < n; i++) {
if(i != 0) {
sum = max(sum - abs(v[i].fi - v[i-1].fi), 0LL);
}
sum += v[i].se;
ans = max(ans, sum);
}
cout << ans << endl;
}
