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 <string>
#include <sstream>
#include <map>
#include <queue>
using namespace std;

#define REP(i,n,m) for(int i=n;i<m;i++)
#define rep(i,n) REP(i,0,n)

class State{
public:
	string s;
	int cost;
	int idx[2];

	State(string ts,int tcost,int tidx[]){
		s = ts;
		cost = tcost;
		idx[0] = tidx[0];
		idx[1] = tidx[1];
	}
};

int di[13][4] = {
	{-1,-1,2,-1},
	{-1,2,5,-1},
	{0,3,6,1},
	{-1,-1,7,2},
	{-1,5,-1,-1},
	{1,6,9,4},
	{2,7,10,5},
	{3,8,11,6},
	{-1,-1,-1,7},
	{5,10,-1,-1},
	{6,11,12,9},
	{7,-1,-1,10},
	{10,-1,-1,-1},
};

void printPuzzle(string s){
	cout<<"  "<<s.substr(0,1)<<endl;
	cout<<" "<<s.substr(1,3)<<endl;
	cout<<s.substr(4,5)<<endl;
	cout<<" "<<s.substr(9,3)<<endl;
	cout<<"  "<<s.substr(12,1)<<endl;
	cout<<"----------------------------\n";
}

queue<State> open;
map<string,int> closed,closed2;

int main(void){
	string alpha = "abcdefghijkl";
	int idx[] = {0,12};

	open.push(State("abcdefghijkla",0,idx));
	closed.insert(pair<string,int>("abcdefghijkla",0));

	while(!open.empty()){
		State st = open.front(); open.pop();
		if(st.cost >= 14) continue;

		rep(i,2){
			rep(j,4){
				int to = di[st.idx[i]][j];
				if(to == -1) continue;

				string res = st.s;
				int tmp = res[st.idx[i]];
				res[st.idx[i]] = res[to];
				res[to] = tmp;

				if(closed.find(res) == closed.end()){
					idx[0] = i==0 ? to : st.idx[0];
					idx[1] = i==1 ? to : st.idx[1];
					open.push(State(res,st.cost+1,idx));
					closed.insert(pair<string,int>(res,st.cost+1));
				}
			}
		}
	}

	while(1){
		int x;
		cin>>x;
		if(x == -1) break;

		stringstream ss;
		ss<<alpha[x];
		rep(i,12){
			cin>>x;
			ss<<alpha[x];
		}

		string start = ss.str();

		while(!open.empty()) open.pop();
		closed2.clear();

		for(idx[0]=0;start[idx[0]]!='a';idx[0]++);
		for(idx[1]=start.length()-1;start[idx[1]]!='a';idx[1]--);
		open.push(State(start,0,idx));
		closed2.insert(pair<string,int>(start,0));

		int ans = -1;

		while(!open.empty()){
			State st = open.front(); open.pop();
			if(closed.find(st.s) != closed.end() && st.cost + closed[st.s] <= 20){
				ans = st.cost + closed[st.s];
				break;
			}
			if(st.cost >= 7) continue;

			rep(i,2){
				rep(j,4){
					int to = di[st.idx[i]][j];
					if(to == -1) continue;

					string res = st.s;
					int tmp = res[st.idx[i]];
					res[st.idx[i]] = res[to];
					res[to] = tmp;

					if(closed2.find(res) == closed2.end()){
						idx[0] = i==0 ? to : st.idx[0];
						idx[1] = i==1 ? to : st.idx[1];
						open.push(State(res,st.cost+1,idx));
						closed2.insert(pair<string,int>(res,st.cost+1));
					}
				}
			}
		}

		if(ans == -1) cout<<"NA\n";
		else cout<<ans<<endl;
	}

	return 0;
}