#include <bits/stdc++.h>
using namespace std;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(NULL);
int N; cin >> N;
map<long long, long long> A;
for (int i = 0; i < N; i++) {
long long a, b; cin >> a >> b;
if (A.count(a)) A[a] += b;
else A.insert({a, b});
}
N = A.size();
vector<long long> aus, h;
for (auto i : A) {
aus.push_back(i.second);
h.push_back(i.first);
}
aus.push_back(0);
for (int i = N-1; i >= 0; i--) aus[i] += aus[i+1];
vector<long long> mass(N);
mass[0] = aus[0]+h[0];
for (int i = 1; i < N; i++) {
mass[i] = max(mass[i-1], aus[i]+h[i]);
}
long long best = -1000000000000000;
for (int i = 0; i < N; i++) {
best = max(best, mass[i]-h[i]-aus[i+1]);
}
cout << best << "\n";
}
