#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <set>
#define DEBUG 1
using namespace std;
int main ( int argc , char * argv[] ) {
multiset<int> set;
multiset<int> :: iterator f,r;
int n;
long long int cost = 0;
scanf("%d" , &n);
while ( n-- ) {
int k;
scanf("%d" , &k);
int i = 0;
for ( i = 0 ; i < k ; i++ ) {
int x;
scanf("%d" , &x);
set.insert(x);
}
f = set.begin();
r = set.end();
r --;
cost += (*r - *f);
set.erase(f);
set.erase(r);
}
cout << cost << endl;
return 0;
}
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