#include "bits/stdc++.h"
 
using namespace std;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef vector<PII> VPII;
typedef long long LL;
typedef priority_queue<int> PQ_DESC;
typedef priority_queue<int, vector<int>, greater<int>> PQ_ASC;
typedef priority_queue<PII> PQ_DESC_PII;
typedef priority_queue<PII, vector<PII>, greater<PII>> PQ_ASC_PII;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef vector<VVLL> VVVLL;

#define SORT_ASC(c) sort((c).begin(), (c).end())
#define SORT_DESC(c) sort((c).begin(), (c).end(), greater<typeof((c).begin())>())
 
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define FORL(i,a,b) for(LL i=(a);i<(b);++i)
#define REPL(i,n)  FORL(i,0,n)
#define ALL(a) (a).begin(),(a).end()
 
const double EPS = 1e-10;
const double PI  = acos(-1.0);

 //debug func
template<typename T>
void vprint(vector<T> v) {
    for(auto x : v) {
        cerr << x << " ";
    }
    cerr << endl;
}
 
template<typename T>
void vvprint(vector<vector<T>> vv) {
    REP(i, vv.size()) {
        REP(j, vv[i].size()) {
            cerr << vv[i][j] << " ";
        }
        cerr << endl;
    }
}

template <typename Iterator>
inline bool next_combination(const Iterator first, Iterator k, const Iterator last)
{
   /* Credits: Thomas Draper */
   if ((first == last) || (first == k) || (last == k))
      return false;
   Iterator itr1 = first;
   Iterator itr2 = last;
   ++itr1;
   if (last == itr1)
      return false;
   itr1 = last;
   --itr1;
   itr1 = k;
   --itr2;
   while (first != itr1)
   {
      if (*--itr1 < *itr2)
      {
         Iterator j = k;
         while (!(*itr1 < *j)) ++j;
         iter_swap(itr1,j);
         ++itr1;
         ++j;
         itr2 = k;
         rotate(itr1,j,last);
         while (last != j)
         {
            ++j;
            ++itr2;
         }
         rotate(k,itr2,last);
         return true;
      }
   }
   rotate(first,k,last);
   return false;
}

inline double get_time_sec(void){
    return static_cast<double>(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count())/1000000000;
}

template<typename T>
T lcm(T a, T b) {
    return (a / __gcd(a, b)) * b;
}

template<typename T>
map<T, T> prime_list(T n) {
    map<T, T> ret;
    for(T i = 2; i*i <= n; i++) {
        if(n % i == 0) {
            ret[i] = 0;
            while(n % i == 0) {
                n /= i;
                ret[i]++;
            }
        }
    }
    if(n != 1) ret[n]++;
    return ret;
}

#define MOD 1000000007

LL mypow(LL a, LL n) {
    if(n == 0) return 1;
    if(n == 1) return a % MOD;
    if(n % 2 == 1) return (a * mypow(a, n-1)) % MOD;
    LL t = mypow(a, n/2);
    return (t * t) % MOD; 
}

LL mycomb(LL n, LL k) {
    if(n == 0 || n == k) return 1;
    LL x = 1, y = 1;
    REP(i, k) {
        x = x * (n-i) % MOD;
        y = y * (i+1) % MOD;
    }
    return x * mypow(y, MOD - 2) % MOD;
}

#define INF 1e8

struct edge {int u, v, cost;};

vector<edge> g;
VI par, rnk;

int root(int x) {
    if(par[x] == x) return x;
    else return par[x] = root(par[x]);
}

int same(int x, int y) {
    x = root(x);
    y = root(y);
    return x == y;
}

void unite(int x, int y) {
    x = root(x);
    y = root(y);
    if(rnk[x] > rnk[y]) {
        par[y] = x;
    } else {
        par[x] = y;
        if(rnk[x] == rnk[y]) rnk[y]++;
    }
}

int main(void) {
    cin.tie(0); ios::sync_with_stdio(false);
    VVI b(3, VI(3));
    REP(i, 3) REP(j, 3) cin >> b[i][j];
    VVI c = {{1, 2, 3}, {4, 5, 6}, {7, 8, 0}};
    if(b == c) {cout << 0 << endl; return 0;}
    map<VVI, int> mb;
    queue<VVI> q;
    q.push(b);
    while(!q.empty()) {
        auto p = q.front();
        q.pop();
        int i, j;
        REP(_i, 3) REP(_j, 3) if(p[_i][_j] == 0) {
            i = _i;
            j = _j;
        }
        if(i > 0) {
            VVI c(p);
            swap(c[i-1][j], c[i][j]);
            if(!mb[c]) {
                mb[c] = mb[p] + 1;
                q.push(c);
            } 
        }
        if(i < 2) {
            VVI c(p);
            swap(c[i][j], c[i+1][j]);
            if(!mb[c]) {
                mb[c] = mb[p] + 1;
                q.push(c);
            } 
        }
        if(j > 0) {
            VVI c(p);
            swap(c[i][j-1], c[i][j]);
            if(!mb[c]) {
                mb[c] = mb[p] + 1;
                q.push(c);
            } 
        }
        if(j < 2) {
            VVI c(p);
            swap(c[i][j], c[i][j+1]);
            if(!mb[c]) {
                mb[c] = mb[p] + 1;
                q.push(c);
            } 
        }
        if(mb[{{1, 2, 3}, {4, 5, 6}, {7, 8, 0}}]) {
            cout << mb[{{1, 2, 3}, {4, 5, 6}, {7, 8, 0}}] << endl;
            return 0;
        }
    }
}


Measured memory_bytes: 49316