Go: // n×nの成長度表に現れる数字を重複を許してm-1個選んで掛け合わせる時の最大値を求める
// ->掛け算型のDP

package main

import (
	"bufio"
	"os"
	"strings"
	"strconv"
		"fmt"
)

var scanner = bufio.NewScanner(os.Stdin)

func main() {
	for scanner.Scan(){
		buf := strings.Split(scanner.Text(), " ")
		n, _ := strconv.Atoi(buf[0])
		m, _ := strconv.Atoi(buf[1])
		if n == 0 && m == 0 {
			break
		}
		growth_table := make([][]float64, n)
		for i := range growth_table {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			tmp := make([]float64, n)
			for j := range tmp {
				tmp[j], _ = strconv.ParseFloat(buf_[j], 64)
			}
			growth_table[i] = tmp
		}
		dp := make([][]float64, m)
		for i := range dp {
			dp[i] = make([]float64, n)
		}
		for i := range dp {
			dp[0][i] = 1
		}
		for k := 1; k < m; k++ {
			// k個使うとき...
			for i := 0; i < n; i++ {
				for j := 0; j < n; j++ {
					// 新たにgrowth_table[i][jを使うかどうか
					dp[k][j] = max(dp[k][j], dp[k-1][i]*growth_table[i][j])
					// check(dp)
				}
			}
		}
		ans := 0.0
		for i := 0; i < n; i++ {
			if dp[m-1][i] > ans {
				ans = dp[m-1][i]
			}
		}
		fmt.Printf("%.2f\n", ans)
	}
}

func max(a, b float64) float64 {
	if a < b {
		return b
	}
	return a
}

// func check(dp [][]float64) {
// 	log.Println()
// 	for i := range dp {
// 		log.Println(dp[i])
// 	}
// 	log.Println()
// }

C++: #include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <algorithm>
#include <vector>
#include <utility>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <functional>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
 
using namespace std;
 
#define rep(i,n) for(int i=0; i<(n); i++)
#define repc(i,s,e) for(int i=(s); i<(e); i++)
#define pb(n) push_back((n))
#define mp(n,m) make_pair((n),(m))
#define all(r) r.begin(),r.end()
#define fi first
#define se second
 
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vii;
typedef vector<ll> vl;
typedef vector<vl> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

typedef pair<int, pii> pip;
 
 
 
const int INF = 1000000;
const double EPS = 1e-8;
const int mod = 1e9 + 7;

double d[1000][1000];
double dp[1000][1000];

int main(){
	int n, m;
	while(cin>>n>>m){
		if(n == 0 && m == 0) break;
		for(int i = 0; i <= n; i++){
			dp[0][i] = 1.0;
		}
		for(int i = 0; i < n; i++){
			for(int j = 0; j < n ; j++){
				cin>>d[i][j];
			}
		}
		for(int i = 1; i < m; i++){
			for(int j = 0; j < n; j++){
				dp[i][j] = -1.0;
				for(int k = 0; k < n; k++){
					dp[i][j] = max(dp[i][j], dp[i-1][k]*d[k][j]);
				}
			}
		}
		double ans = -1;
		for(int i= 0; i < n; i++){
			ans = max(dp[m-1][i], ans);
		}
		printf("%.2lf\n", ans);
	}
}

C++: #include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<cctype>
#include<complex>
#include<iostream>
#include<sstream>
#include<algorithm>
#include<functional>
#include<utility>
#include<vector>
#include<string>
#include<stack>
#include<queue>
#include<map>
#include<set>
 
using namespace std;
const int dx[] = {1,0,-1,0},dy[] = {0,1,0,-1};
#define INF 1e+9
#define EPS 1e-9
#define rep(i,j) for(int i = 0; i < (j); i++)
#define reps(i,j,k) for(int i = j; i < (k); i++)
typedef long long ll;
double fert[128][128];
double dp[128][128];
int main(){
    int n,m;
    while(scanf("%d%d",&n,&m),(n|m)){
        memset(dp,0,sizeof(dp));
        rep(i,n)rep(j,n)scanf("%lf",&fert[i][j]);
        rep(i,m){
            rep(j,n){
                if(i == 0)dp[i][j] = 1.00;
                else{
                    rep(k,n){
                        dp[i][j] = max(dp[i][j],dp[i-1][k] * fert[k][j]);
                    }
                }
            }
        }
        double res = -1.0;
        rep(i,n){
            res = max(res,dp[m-1][i]);
        }  
        printf("%lf\n",res);
    }
    return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <cstdio>
using namespace std;
#define MAX 101

int main(){
  double dp[MAX][MAX],nae[MAX][MAX];
  int n,m;

  while(cin >> n >> m, n+m){
    fill(dp[0],dp[MAX-1],1);

    for(int i = 0 ; i < n ; i++)
      for(int j = 0 ; j < n ; j++)
	cin >> nae[i][j];

    for(int i = 1 ; i < m ; i++)
      for(int j = 0 ; j < n ; j++)
	for(int k = 0 ; k < n ; k++)
	  dp[i][j] = max(dp[i][j],dp[i-1][k]*nae[j][k]);

    double ans = 0;
    for(int i = 0 ; i < n ; i++)
      for(int j = 0 ; j < n ; j++)
	ans = max(ans,dp[i][j]);

    printf("%.2f\n" , ans);
  }

  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;

int main() {
  double f[101][101];
  double dp[101][101];
  int n,m;
  while (cin >> n >> m,n||m) {
    
    for ( int i = 0; i < n; i++ ) {
      for ( int j = 0; j < n; j++ ) {
	cin >> f[i][j];
      }
    }

    for ( int i = 0; i < m; i++ ) {
      for ( int j = 0; j < n; j++ ) {
	dp[i][j] = 0.0;
      }
    }

    for ( int i = 0; i < n; i++ ) dp[0][i] = 1.0;

    for ( int i = 1; i < m; i++ ) {
      for ( int j = 0; j < n; j++ ) {
	for ( int k = 0; k < n; k++ ) {
	  dp[i][j] = max( dp[i][j], dp[i-1][k] * f[j][k] );
	}
      }
    }

    double ans = 0.0;
    for ( int i = 0; i < n; i++ ) {
      ans = max ( ans, dp[m-1][i] );
    }
      
    printf ("%.2f\n", ans );
  }
  return 0;
}

C++: #define _USE_MATH_DEFINES
#define INF 10000000
#include <iostream>
#include <sstream>
#include <cmath>
#include <algorithm>
#include <queue>
#include <stack>
#include <limits>
#include <map>
#include <string>
#include <cstring>
#include <set>
#include <deque>
#include <bitset>

using namespace std;

typedef long long ll;
typedef pair<int,string> P;

static const double eps = 1e-8;

double dp[101][101];
double table[100][100];

int main(){

	int n,m;
	while(~scanf("%d %d",&n,&m)){
		if(n==m && m==0) break;
		for(int y=0;y<n;y++){
			for(int x=0;x<n;x++){
				scanf("%lf",&table[y][x]);
			}
		}

		fill((double*)dp,(double*)dp+101*101,1.0);

		for(int k=0;k<m;k++){
			for(int i=0;i<n;i++){
				for(int j=0;j<=i;j++){
					dp[i][k+1] = max(max(dp[i][k]*table[i][j],dp[i][k]*table[j][i]),dp[i][k+1]);
				}
			}
		}

		printf("%.2lf\n",dp[n-1][m-1]);
	}
}

C++: #include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstring>
#include <sstream>
#include <cassert>
using namespace std;
static const double EPS = 1e-5;
typedef long long ll;
typedef pair<int,int> PI;
typedef vector<int> vi;
#define rep(i,n) for(int i=0;i<(int)n;++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
#define mp make_pair
#define pb push_back
#define F first
#define S second

const int MAX=100;

int main(void)
{
  int n,m,i,j,k;
  double g[MAX][MAX+1],dp[MAX][MAX+1],res;//mñÚ,níÞ
  for(;;){
    scanf("%d%d",&n,&m); if(!n)break;
    rep(i,n)dp[0][i]=1.0;
    rep(i,n)rep(j,n)scanf("%lf",g[i]+j);
    rep(i,m)rep(j,n)rep(k,n){
      dp[i+1][j]=max(dp[i+1][j],dp[i][k]*g[j][k]);
    }
    res=0;
    rep(i,m)res=max(res,dp[i][n-1]);
    printf("%.2f\n",res);
  }
  return 0;
}