#include<bits/stdc++.h>
using namespace std;
#define ll long long
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
ll n; cin >> n;
map<ll, ll> size_to_value;
ll a, b;
for (ll i=0; i<n; i++) {
cin >> a >> b;
size_to_value[a] += b;
}
vector<ll> A, B;
for (const auto &[key, value] : size_to_value) {
A.push_back(key);
B.push_back(value);
}
n = size_to_value.size();
vector<ll> ps_B (n+1, 0);
for (ll i=0; i<n; i++) {
ps_B[i+1] = ps_B[i] + B[i];
}
// O(n^2) algorithm
ll ans = LLONG_MIN;
for (ll i=0; i<n; i++) {
ll A_min = A[i];
for (ll j=i; j<n; j++) {
ll A_max = A[j];
ll S = ps_B[j+1] - ps_B[i];
ll score = S - (A_max - A_min);
ans = max(ans, score);
}
}
cout << ans << "\n";
return 0;
}
