#include <iostream>
#include<cstdio>
using namespace std;
double bi(double a,double b){
    if(a==0) return b;
    if(b==0) return a;
    return a<b? a:b;
}
int main()
{
    int n, m, a[101][101] = { 0 },ge[101]={0};//a[i][j] i-->j 的直飞路径，已用优惠券数
    double f[101][21] = { 0 };//距离1最短距离，已用优惠券数
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            cin >> a[i][j];
        }
    }
    for (int i = 1; i <= n; i++) {
        f[i][0] = a[1][i];
        f[i][1] = a[1][i] / 2;
        ge[i]=1;
    }
    //重复n次保证全部轮过
    for (int e = 1; e <= n; e++) {
        //当前起点
        for (int i = 1; i <= n; i++) {
            //当前终点
            if (f[i][0] > 0) {
                for (int j = 1; j <= n; j++) {
                    if (a[i][j] > 0) {
                        if(ge[i]+1<=m) ge[i]++;
                        for (int k = 0; k <= ge[i]; k++) {
                            f[j][k]=bi(f[j][k],f[i][k]+a[i][j]);
                            if(k!=m){
                                f[j][k+1]=bi(f[j][k+1],f[i][k]+a[i][j]/2);
                                f[j][k+1]=bi(f[j][k],f[j][k+1]);
                            }
                        }
                    }
                }
            }
        }
    }
    double ans=f[n][0];
    for(int i=1;i<=m;i++){
        if(ans>f[n][i]&&f[n][i]!=0){
            ans=f[n][i];
        }
    }
    printf("%0.1f",ans);
}