BFS.
import java.util.*;
class Main{
static class node{
int x;
int y;
int cnt;
String s;
String s1;
public node(int x, int y, int cnt,String s,String s1) {
this.x = x;
this.y = y;
this.cnt = cnt;
this.s=s;
this.s1=s1;
}
}
static int dx[]= {0,0,1,-1};
static int dy[]= {1,-1,0,0};
static char a[][]=new char [3][3];
static String ans=”12345678x”;
static int vis[][][];
static String state=”“;
static boolean flag=true;
public static void main(String[] args) {
Scanner in =new Scanner(System.in);

    for(int i=0;i<3;i++) {
        for(int j=0;j<3;j++) {
            String s=in.next();
            a[i][j]=s.charAt(0);
            state+=a[i][j];
        }
    }
    vis=new int [3][3][100];
        bfs();
        if(flag) {
            System.out.println("unsolvable");
        }

}
static String p="rldu";
static Set<String> set=new HashSet<String>();
static void bfs() {
    Queue<node> q=new ArrayDeque<Main.node>();
    int k=0;

    for(int i=0;i<state.length();i++) {
        if(state.charAt(i)=='x') {
            k=i;
        }
    }
    set.add(state);
    q.add(new node(k/3,k%3,0,state,""));
    vis[k/3][k%3][0]=1;
    while(!q.isEmpty()) {
        node u=q.peek();
        q.poll();
        set.add(u.s);
        if(u.s.equals(ans)) {
            flag=false;
            System.out.println(u.s1);
            break;
        }
        for(int i=0;i<dx.length;i++) {
            int x=u.x+dx[i];
            int y=u.y+dy[i];
            if(x>=0&&y>=0&&x<3&&y<3) {
                char c[]=u.s.toCharArray();
                char t=c[3*x+y];
                c[3*x+y]=c[3*u.x+u.y];
                c[3*u.x+u.y]=t;
                if(set.contains(new String(c))) {
                    continue;
                }
                q.add(new node(x,y,u.cnt+1,new String(c),u.s1+p.charAt(i)));
            }
        }
    }
}

}