#include <iostream>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <ctime>
#include <cstring>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <bitset>
#include <numeric>
#include <utility>
#include <iomanip>
#include <algorithm>
#include <functional>
using namespace std;

typedef long long ll;
typedef vector<int> vint;
typedef vector<long long> vll;
typedef pair<int,int> pint;
typedef pair<long long, long long> pll;

#define MP make_pair
#define PB push_back
#define ALL(s) (s).begin(),(s).end()
#define EACH(i, s) for (__typeof__((s).begin()) i = (s).begin(); i != (s).end(); ++i)
#define COUT(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << endl

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T1, class T2> ostream& operator << (ostream &s, pair<T1,T2> P) 
{ return s << '<' << P.first << ", " << P.second << '>'; }
template<class T> ostream& operator << (ostream &s, vector<T> P) 
{ for (int i = 0; i < P.size(); ++i) { if (i > 0) { s << " "; } s << P[i]; } return s; }
template<class T1, class T2> ostream& operator << (ostream &s, map<T1,T2> P) 
{ EACH(it, P) { s << "<" << it->first << "->" << it->second << "> "; } return s; }


const int INF = 1<<29;
int n, m, c, l, w;
vector<pint> data[200];

int dp[160][15][100];

int main() {
    while (cin >> n >> m) {
        if (n == 0) break;
        
        for (int i = 0; i < 200; ++i) data[i].clear();
        for (int i = 0; i < n; ++i) {
            cin >> c;
            for (int j = 0; j < c; ++j) {
                cin >> l >> w;
                data[i].PB(pint(l,w));
            }
        }
        
        
        for (int j = 0; j < 15; ++j) for (int k = 0; k < 100; ++k) {
            for (int i = 0; i < 160; ++i) dp[i][j][k] = INF;
        }
        for (int i = 0; i < data[0].size(); ++i) dp[0][i][0] = 0;
        for (int i = 0; i < data[1].size(); ++i) dp[1][i][1] = 0;
        
        int res = INF;
        for (int i = 0; i < n-1; ++i) {
            for (int j = 0; j < data[i].size(); ++j) {
                
                // 1行
                for (int k = 0; k < data[i+1].size(); ++k) {
                    int add = (data[i][j].second + data[i+1][k].second) * abs(data[i][j].first - data[i+1][k].first);
                    for (int l = 0; l <= m; ++l) {
                        chmin(dp[i+1][k][l], dp[i][j][l] + add);
                    }
                }
                
                // 2行
                if (i < n-2) {
                    for (int k = 0; k < data[i+2].size(); ++k) {
                        int add = (data[i][j].second + data[i+2][k].second) * abs(data[i][j].first - data[i+2][k].first);
                        for (int l = 0; l < m; ++l) {
                            chmin(dp[i+2][k][l+1], dp[i][j][l] + add);
                        }
                    }
                }
            }
        }
        
        for (int j = 0; j <= 15; ++j) for (int k = 0; k <= m; ++k) chmin(res, dp[n-1][j][k]);
        for (int j = 0; j <= 15; ++j) for (int k = 0; k <= m-1; ++k) chmin(res, dp[n-2][j][k]);
        
        cout << res << endl;
    }
    return 0;
}


Measured memory_bytes: 2164