#include <iostream>

#include <set>

using namespace std;

int main()

{

	ios_base::sync_with_stdio(false);

	cin.tie(nullptr);

	cout.tie(nullptr);

	int n, k, temp;

	unsigned long long total;

	multiset<int> bill;

	while (cin >> n && n) {

		total = 0;

		bill.clear();

		while (n--) {

			cin >> k;

			for (size_t i = 0; i < k; i++) cin >> temp, bill.emplace(temp);

			total += *bill.rbegin() - *bill.begin();

			bill.erase(bill.begin());

			auto it = bill.end();

			bill.erase(--it);

		}

		cout << total << "\n";

	}

	return 0;

}