#include<iostream>
#include<cmath>
#include<string>
#include<map>
#include<queue>
using namespace std;
#define N 3
#define N2 9
struct Puzzle{
  int f[N2];
  int space;
  string path;
  bool operator<(const Puzzle &p)const{
    for(int i=0;i<N2;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',};

bool isTarget(Puzzle p){
  for(int i=0;i<N2;i++)
    if(p.f[i]!=(i+1))return false;
  return true;
}

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

  while(!Q.empty()){
    u=Q.front();
    Q.pop();
    if(isTarget(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;
      swap(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(int i=0;i<N2;i++){
    cin>>in.f[i];
    if(in.f[i]==0){
      in.f[i]=N2;
      in.space=i;
    }
  }
  string ans=bfs(in);
  cout<<ans.size()<<endl;
  return 0;
}

