#include <bits/stdc++.h>

using namespace std;

int main() {
    int N, P;
    cin >> N >> P;
    int a[N], b[N], c[N];
    int i, j, k;
    for(i = 0; i < N; i++) {
        cin >> a[i] >> b[i] >> c[i];
    }

    int dp[N + 1][P + 1]; //N個目までのコンテストでP問解答した時の順位の和
    for(i = 0; i <= N; i++) {
        for(j = 0; j <= P; j++) {
            dp[i][j] = 1000000.0;
        }
    }
    dp[0][0] = 0;

    for(i = 0; i < N; i++) {
        for(j = 0; j <= P; j++) {
            dp[i + 1][j] = dp[i][j] + a[i];
            if(j>0)dp[i + 1][j] = min(dp[i + 1][j], dp[i][j - 1] + b[i]);
            if(j>1)dp[i + 1][j] = min(dp[i + 1][j], dp[i][j - 2] + c[i]);
            if(j>2)dp[i + 1][j] = min(dp[i + 1][j], dp[i][j - 3] + 1);
        }
    }
    printf("%.6f\n",(double)dp[N][P] / N);
    return 0;
}