Go: // BFS

package main

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

var scanner = bufio.NewScanner(os.Stdin)

var p = [15]int{}
var g = [13][4]int {
	// -1は存在しないマス目
	{2,-1,-1,-1},
	{2,5,-1,-1},{0,1,3,6},{2,7,-1,-1},
	{5,-1,-1,-1},{1,4,6,9},{2,5,7,10},{3,6,8,11},{7,-1,-1,-1},
	{5,10,-1,-1},{6,9,11,12},{7,10,-1,-1},
	{10,-1,-1,-1},
}

/*
　  ０ １ ２ ３ ４
 0 |／|／|  |／|／|
 1 |／|　|  |　|／|
 2 |　|　|  |　|　|
 3 |／|　|  |　|／|
 4 |／|／|  |／|／|
*/

var row = [13]int{0,1,1,1,2,2,2,2,2,3,3,3,4}
var col = [13]int{2,1,2,3,0,1,2,3,4,1,2,3,2}

type wolf struct {
	m [13]int
}

type pair struct {
	first wolf
	second int
}

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

func print_board(board [13]int) {
	fmt.Println("--------------------------")
	fmt.Printf("        [%2d]\n", board[0])
	fmt.Printf("    [%2d][%2d][%2d]\n", board[1], board[2], board[3])
	fmt.Printf("[%2d][%2d][%2d][%2d][%2d]\n", board[4], board[5], board[6], board[7], board[8])
	fmt.Printf("    [%2d][%2d][%2d]\n", board[9], board[10], board[11])
	fmt.Printf("        [%2d]\n", board[12])
	fmt.Println("--------------------------")
}

func main() {
	for scanner.Scan() {
		p1, _ := strconv.Atoi(scanner.Text())
		if p1 == -1 {
			break
		}
		p[0]= p1
		scanner.Scan()
		buf1 := strings.Split(scanner.Text(), " ")
		p2, _ := strconv.Atoi(buf1[0])
		p3, _ := strconv.Atoi(buf1[1])
		p4, _ := strconv.Atoi(buf1[2])
		p[1], p[2], p[3] = p2, p3, p4
		scanner.Scan()
		buf2 := strings.Split(scanner.Text(), " ")
		p5, _ := strconv.Atoi(buf2[0])
		p6, _ := strconv.Atoi(buf2[1])
		p7, _ := strconv.Atoi(buf2[2])
		p8, _ := strconv.Atoi(buf2[3])
		p9, _ := strconv.Atoi(buf2[4])
		p[4], p[5], p[6], p[7], p[8] = p5, p6, p7, p8, p9
		scanner.Scan()
		buf3 := strings.Split(scanner.Text(), " ")
		p10, _ := strconv.Atoi(buf3[0])
		p11, _ := strconv.Atoi(buf3[1])
		p12, _ := strconv.Atoi(buf3[2])
		p[9], p[10], p[11] = p10, p11, p12
		scanner.Scan()
		p13, _ := strconv.Atoi(scanner.Text())
		p[12] = p13
		S := make(map[wolf]struct{})
		st := wolf{}
		for i := 0; i < 13; i++ {
			st.m[i] = p[i]
		}
		Q := make([]pair, 0)
		S[st] = struct{}{}
		Q = append(Q, pair{st, 0})
		yet := true
		for len(Q) > 0 {
			at := Q[0].first
			// print_board(at.m)
			cost := Q[0].second
			Q = Q[1:]
			ok := true
			for i :=1; i < 12; i++ {
				if at.m[i] != i {
					ok = false
				}
			}
			if ok {
				// print_board(at.m)
				yet = false
				fmt.Println(cost)
				break
			}
			now := cost
			for i := 0; i < 13; i++ {
				if at.m[i] != 0 {
					now += abs(row[i]-row[at.m[i]]) + abs(col[i]-col[at.m[i]])
				}
			}
			if now > 20 {
				continue
			}
			for i := 0; i < 13; i++ {
				if at.m[i] == 0 {
					for j := 0; j < 4; j++ {
						if ^g[i][j] != 0 {
							at.m[i], at.m[g[i][j]] = at.m[g[i][j]], at.m[i]
							if _, ok := S[at]; !ok {
								S[at] = struct{}{}
								Q = append(Q, pair{at, cost+1})
							}
							at.m[i], at.m[g[i][j]] = at.m[g[i][j]], at.m[i]
						}
					}
				}
			}
		}
		if yet {
			fmt.Println("NA")
		}
	}
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#define lol(i,n) for(int i=0;i<n;i++)
#define mod 1000000007
typedef long long ll;
using namespace std;
int dx[13][4]={
  {3,0,0,0},
  {3,6,0,0},
  {1,2,4,6},
  {3,8,0,0},
  {6,0,0,0},
  {2,5,7,10},
  {3,6,8,11},
  {4,7,9,12},
  {8,0,0,0},
  {6,11,0,0},
  {6,10,12,13},
  {8,11,0,0},
  {11,0,0,0}
};
map<ll,int> mp;
ll Compress(int p[]){
  ll ans=0;
  for(int i=0;i<13;i++){
    ans*=13;
    ans+=p[i];
  }
  return ans;
}

int unzip[13];
void Unzip(ll x){
  for(int i=0;i<13;i++){
    unzip[12-i]=x%13;
    x/=13;
  }
}

int beflen=0;
queue<pair<ll,int> >Q;
void BFS(int p[],int len){
  //if(len!=beflen){cout<<len<<endl;beflen=len;}
  ll tmp=Compress(p);
  mp[tmp]=len;
  if(len==21)return;
  lol(i,13){
    if(p[i]==0){
      lol(j,4){
	int t=dx[i][j];
	if(t==0)break;
	t--;
	if(p[t]!=0){
	  swap(p[i],p[t]);
	  tmp=Compress(p);
	  if(mp[tmp]!=0)continue;
	  mp[tmp]=-1;
	  Q.push(make_pair(tmp,len+1));
	  swap(p[i],p[t]);
	}
      }
    }
  }
}
int main(){
  int p[13];
  lol(i,13)p[i]=i;p[12]=0;
  Q.push(make_pair(Compress(p),1));
  while(!Q.empty()){
    ll data=Q.front().first;
    int len=Q.front().second;
    Q.pop();
    if(mp[data]>0)continue;
    Unzip(data);
    BFS(unzip,len);
  }
  while(cin>>p[0]&&p[0]!=-1){
    for(int i=1;i<13;i++)cin>>p[i];
    ll tmp=Compress(p);
    int cost=mp[tmp];
    if(cost==0)cout<<"NA"<<endl;
    else cout<<cost-1<<endl;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

const int INF = 1<<28;
const int H = 5;
const int W = 5;

struct State {
  int g[H][W];
  int x[2], y[2];
  bool operator < (const State &s) const {
    for(int i = 0; i < H; ++i) {
      for(int j = abs(2-i); j < W-abs(2-i); ++j) {
        if(g[i][j] != s.g[i][j]) return g[i][j] < s.g[i][j];
      }
    }
    return false;
  }
  bool operator == (const State &s) const {
    return !(*this < s) && !(s < *this);
  }
};

map<State,int> bfs1(State src) {
  const static int dx[4] = {1,0,-1,0};
  const static int dy[4] = {0,1,0,-1};
  map<State,int> cost;
  queue<State> que;
  cost[src] = 0;
  que.push(src);
  while(que.size()) {
    const State s = que.front();
    que.pop();
    if(cost[s] == 11) continue;
    for(int k = 0; k < 2; ++k) {
      for(int i = 0; i < 4; ++i) {
        int nx = s.x[k] + dx[i];
        int ny = s.y[k] + dy[i];
        if(nx < 0 || nx >= W) continue;
        if(ny < 0 || ny >= H) continue;
        if(s.g[ny][nx] <= 0) continue;
        State t = s;
        swap(t.g[t.y[k]][t.x[k]], t.g[ny][nx]);
        t.x[k] = nx;
        t.y[k] = ny;
        if(cost.count(t)) continue;
        cost[t] = cost[s] + 1;
        que.push(t);
      }
    }
  }
  return cost;
}

int bfs2(State src, map<State,int> rcost) {
  const static int dx[4] = {1,0,-1,0};
  const static int dy[4] = {0,1,0,-1};
  if(rcost.count(src)) return rcost[src];
  map<State,int> cost;
  queue<State> que;
  cost[src] = 0;
  que.push(src);
  while(que.size()) {
    const State s = que.front();
    que.pop();
    if(cost[s] == 11) continue;
    for(int k = 0; k < 2; ++k) {
      for(int i = 0; i < 4; ++i) {
        int nx = s.x[k] + dx[i];
        int ny = s.y[k] + dy[i];
        if(nx < 0 || nx >= W) continue;
        if(ny < 0 || ny >= H) continue;
        if(s.g[ny][nx] <= 0) continue;
        State t = s;
        swap(t.g[t.y[k]][t.x[k]], t.g[ny][nx]);
        t.x[k] = nx;
        t.y[k] = ny;
        if(cost.count(t)) continue;
        cost[t] = cost[s] + 1;
        que.push(t);
        if(rcost.count(t)) {
          return cost[t] + rcost[t];
        }
      }
    }
  }
  return INF;
}

int main() {
  State src, dst;
  map<State,int> rcost;
  fill(src.g[0], src.g[H], -1);
  fill(dst.g[0], dst.g[H], -1);
  for(int i = 0, k = 0, t = 0; i < H; ++i) {
    for(int j = abs(2-i); j < W-abs(2-i); ++j) {
      dst.g[i][j] = t % 12;
      ++t;
      if(dst.g[i][j] == 0) {
        dst.x[k] = j;
        dst.y[k] = j;
        ++k;
      }
    }
  }
  rcost = bfs1(dst);
  while(1) {
    for(int i = 0, k = 0; i < H; ++i) {
      for(int j = abs(2-i); j < W-abs(2-i); ++j) {
        cin >> src.g[i][j];
        if(src.g[i][j] == -1) return 0;
        if(src.g[i][j] == 0) {
          src.x[k] = j;
          src.y[k] = i;
          ++k;
        }
      }
    }
    int res = bfs2(src, rcost);
    if(res > 20) cout << "NA" << endl;
    else cout << res << endl;
  }
  return 0;
}