#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int main(void)  {

    int n;

    multiset<int> S;

    while (scanf ("%d", &n) == 1)   {

        if (!n) break;

        S.clear ();

        ll ans = 0;

        for (int m, i=1; i<=n; ++i)    {

            scanf ("%d", &m);

            for (int v, j=1; j<=m; ++j)    {

                scanf ("%d", &v);

                S.insert (v);

            }

            int p1 = *(S.begin ());

            int p2 = *(S.rbegin ());

            ans += p2 - p1;

            S.erase (S.find (p1));

            S.erase (S.find (p2));

        }

        printf ("%I64d\n", ans);

    }

    return 0;

}