//
//
//  Codeforces: ganariya
//  AtCoder: ganariya2525
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//  MMMMMMMMMMMMMMMMNOtXtdMMMMMNxzZMMNmgHyVVVVVW%..?/(.,(x-..........(HfffpffpffpffWHHffpffppfVyyWMMMMMM


//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <unordered_map>
#include <climits>
#include <set>
#include <unordered_set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue>
#include <random>
#include <complex>
#include <regex>
#include <locale>
#include <random>
#include <type_traits>

using namespace std;

#define SHOW_VECTOR(v) {std::cerr << #v << "\t:";for(const auto& xxx : v){std::cerr << xxx << " ";}std::cerr << "\n";}
#define SHOW_MAP(v){std::cerr << #v << endl; for(const auto& xxx: v){std::cerr << xxx.first << " " << xxx.second << "\n";}}

using LL = long long;

//~~~~~~~~~~~~~~~~~~~~~_(＾～＾ ｣ ∠)_~~~~~~~~~~~~~~~~~~~~~

constexpr LL INF = 1e15;

int main() {

    while (true) {

        int n, m;
        cin >> n >> m;

        if (!(n | m)) break;

        vector<vector<int>> pos(n, vector<int>());
        vector<vector<LL>> risk(n, vector<LL>());
        vector<vector<vector<LL>>> dp(n, vector<vector<LL>>());

        for (int i = 0; i < n; i++) {
            int k;
            cin >> k;
            for (int j = 0; j < k; j++) {
                int p, d;
                cin >> p >> d;
                p--;
                pos[i].push_back(p);
                risk[i].push_back(d);
                dp[i].push_back(vector<LL>(m + 1, INF));
            }
        }

        for (int i = 0; i < pos[0].size(); i++) dp[0][i][0] = 0;
        if (m >= 1)for (int i = 0; i < pos[1].size(); i++) dp[1][i][1] = 0;

        //i段目から移動
        for (int i = 0; i < n; i++) {
            //1段先
            if (i < n - 1) {
                for (int l = 0; l <= m; l++) {
                    for (int j = 0; j < pos[i].size(); j++) {
                        for (int k = 0; k < pos[i + 1].size(); k++) {
                            LL from = pos[i][j];
                            LL to = pos[i + 1][k];
                            dp[i + 1][k][l] = min(dp[i + 1][k][l], dp[i][j][l] + (risk[i][j] + risk[i + 1][k]) * abs(from - to));
                        }
                    }
                }
            }

            //2段先
            if (i < n - 2) {
                for (int l = 0; l < m; l++) {
                    for (int j = 0; j < pos[i].size(); j++) {
                        for (int k = 0; k < pos[i + 2].size(); k++) {
                            LL from = pos[i][j];
                            LL to = pos[i + 2][k];
                            dp[i + 2][k][l + 1] = min(dp[i + 2][k][l + 1], dp[i][j][l] + (risk[i][j] + risk[i + 2][k]) * abs(from - to));
                        }
                    }
                }
            }
        }

        LL ans = LONG_LONG_MAX;
        for (int i = 0; i < dp[n - 1].size(); i++) {
            for (int j = 0; j < dp[n - 1][i].size(); j++) {
                ans = min(ans, dp[n - 1][i][j]);
            }
        }
        for (int i = 0; i < dp[n - 2].size(); i++) {
            for (int j = 0; j < (int) dp[n - 2][i].size() - 1; j++) {
                ans = min(ans, dp[n - 2][i][j]);
            }
        }

        cout << ans << endl;

    }

}






































Measured memory_bytes: 4108