#include<iostream>
#include<cmath>
#include<map>
#include<queue>
#include<string>

using namespace std;
#define N 3
#define M 9
 int i,j;
//?§????????????????
struct Puzzle{
  int f[M];
  int space;
  string path;

  bool operator < (const Puzzle &p)const{
    for( i=0;i<M;i++){
      if(f[i]==p.f[i])continue;
      return f[i]>p.f[i];
    }
    return false;
  }
  
};
////

static const int dx[4]={-1,0,1,0};
static const int dy[4]={0,-1,0,1};
static const char dir[4]={'u','l','d','r'};
///
void swapp(int *p,int *q){
  int tmp;
  tmp=*p;
  *p=*q;
  *q=tmp;
}
///
bool Target(Puzzle p){
  for(i=0;i<M;i++)if(p.f[i]!=(i+1))return false;
  return true;

}
///

///
string bfs(Puzzle s){
  map<Puzzle, bool> V;
  Puzzle u,v;
  queue<Puzzle> Q;
  s.path="";
  Q.push(s);
  V[s]=true;

  while(!Q.empty()){
    u=Q.front();
    Q.pop();
    if(Target(u))return u.path;
    int sx=u.space/N;
    int sy=u.space%N;

    for(int r=0;r<4;r++){
      int tx=sx+dx[r];
      int ty=sy+dy[r];
      if(tx<0 || ty<0 || tx>=N || ty>=N)continue;
      v=u;
      swapp(&v.f[u.space],&v.f[tx*N+ty]);
      v.space=tx*N+ty;
      if(!V[v]){
	V[v]=true;
	v.path+=dir[r];
	Q.push(v);
      } 
    }
  }
  return "unsolvable";
}
///

int main(){
  Puzzle in;

  for(i=0;i<M;i++){
    cin >>in.f[i];
    if(in.f[i]==0){
      in.f[i]=M;
      in.space=i;
    }
  }

  string ans=bfs(in);
  cout << ans.size() << endl;
  return 0;

}