#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
int n;
cin >> n;
vector<ll> a(n), b(n);
vector<pair<ll, int>> v;
for (int i = 0; i < n; i++) {
cin >> a[i] >> b[i];
v.push_back({b[i] - a[i], i});
}
sort(v.rbegin(), v.rend());
ll ans = 0, sum = 0, mx = -1e18, mn = 1e18;
for (int i = 0; i < n; i++) {
sum += b[v[i].second];
mx = max(mx, a[v[i].second]);
mn = min(mn, a[v[i].second]);
ans = max(ans, sum - (mx - mn));
}
cout << ans;
}
