#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, x = LLONG_MAX;
// for (ll i=0; i<n; i++) {
// for (ll j=i; j<n; j++) {
// ll score = ps_B[j+1] - A[j] - (ps_B[i] - A[i]);
// ans = max(ans, score);
// }
// }
// O(n) algorithm
ll ans = LLONG_MIN, x = LLONG_MAX;
for (ll i=0; i<n; i++) {
x = min(x, ps_B[i] - A[i]);
ans = max(ans, ps_B[i+1] - A[i] - x);
}
cout << ans << "\n";
return 0;
}
