#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <fstream>
#include <cassert>
#include <cstring>
#include <unordered_set>
#include <unordered_map>
#include <numeric>
#include <ctime>
#include <bitset>
#include <complex>
#include <random>
using namespace std;
#define int long long
const int INF = 1e18 + 239;
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int n;
cin >> n;
vector<pair<int, int>> aw(n);
for (auto &t : aw) {
cin >> t.first >> t.second;
}
sort(aw.begin(), aw.end());
vector<int> a(n);
vector<int> b(n);
for (int i = 0; i < n; i++) {
tie(a[i], b[i]) = aw[i];
}
vector<int> ps(n + 1);
for (int i = 0; i < n; i++) {
ps[i + 1] = ps[i] + b[i];
}
int mval = -INF;
int ans = -INF;
for (int i = 0; i < n; i++) {
mval = max(mval, -ps[i] + a[i]);
ans = max(ans, ps[i + 1] - a[i] + mval);
}
cout << ans << endl;
}
