#include<bits/stdc++.h>
using namespace std;
#define int long long
int32_t main(){
int n; cin >> n;
vector<pair<int,int>> v(n);
for(auto &[a, b] : v) cin >> a >> b;
sort(v.begin(), v.end());
vector<int> sum(n);
for(int i = 0; i < n; ++i){
sum[i] = v[i].second;
if(i > 0) sum[i] += sum[i - 1];
}
int best_ans = LLONG_MIN;
int max_inv = LLONG_MIN;
for(int i = 0; i < n; ++i){
int inv_a = sum[i] - v[i].first;
int inv_b = v[i].first - ((i - 1 < 0)? 0 : sum[i - 1]);
max_inv = max(max_inv, inv_b);
best_ans = max(best_ans, inv_a + max_inv);
}
cout << best_ans << "\n";
}
