// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;



#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)

#define rep(i,n) repl(i,0,n)

#define INF INT_MAX/3

#define N 3

typedef pair<int, int> P;



struct State {

    int g, h;

    string state;

    P blank;

    string path;

    bool operator<(const State &a) const {

        return g + h > a.g + a.h;

    }

};



int d[5] = {-1, 0, 1, 0, -1};

string r[4] = {"D", "R", "U", "L"};

string ans_str = "";

int ans[N][N], puzzle0[N][N], puzzle1[N][N];

set<string> s;

priority_queue<State> next_state;

string path;



bool range(int y, int x) {return 0 <= y && y < N && 0 <= x && x < N;}



int h1() {

    int find = -1;

    while(next_state.size()) {

        State state = next_state.top();

        next_state.pop();

        if (s.count(state.state)) continue; // already search

        s.insert(state.state); // visited



        P blank = state.blank;

        rep(i, 4) {

            int y = d[i] + blank.first, x = d[i + 1] + blank.second; // next blank position

            if (range(y, x)) { // can be replaced

                string tmp = state.state; // next state (string)

                int wrong_place = state.h, p = blank.first * N + blank.second, q = y * N + x;

                if (N < 4) {

                    swap(tmp[p], tmp[q]);

                    wrong_place = wrong_place - (state.state[q] != ans_str[q]) + (state.state[q] != ans_str[p]);

                } else {

                    swap(tmp[2 * p], tmp[2 * q]), swap(tmp[2 * p + 1], tmp[2 * q + 1]);

                    wrong_place = wrong_place - (state.state.substr(2 * q, 2) != ans_str.substr(2 * q, 2))

                    + (state.state.substr(2 * q, 2) != ans_str.substr(2 * p, 2));

                }

                if (s.count(tmp)) continue; // already search



                if (wrong_place == 0) { // answer

                    find = state.g + 1;

                    path = state.path + r[i];

                    break;

                }



                next_state.push(State{state.g + 1, wrong_place, tmp, P(y, x), state.path + r[i]});

            }

        }

        if (find != -1) break; // find an answer

    }

    return find;

}



int main(){

    // create answer's numbers

    iota(ans[0], ans[0] + N * N, 1);

    ans[N - 1][N - 1] = 0;

    // create number

    iota(puzzle0[0], puzzle0[0] + N * N, 0);

    rep(i, N)rep(j, N) cin >> puzzle0[i][j];



    string state = "";

    P blank;

    int manhattan = 0, wrong_place = 0;

    rep(i, N)rep(j, N) {

        state += to_string(puzzle0[i][j]);

        ans_str += to_string(ans[i][j]);



        if(puzzle0[i][j] == 0) blank = P(i, j);

        else {

            int num = puzzle0[i][j] - 1;

            manhattan += (abs(num / N - i) + abs(num % N - j));

            if (puzzle0[i][j] != ans[i][j]) wrong_place++;

        }

    }



    if (manhattan == 0) { // the answer

        cout << 0 << endl;

    } else {

        int steps;

        next_state.push(State{0, wrong_place, state, blank, ""});

        steps = h1();

        cout << steps << endl;

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 1.2548780240127417x):
#include <bits/stdc++.h>

using namespace std;



#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)

#define rep(i,n) repl(i,0,n)

#define INF INT_MAX/3

#define N 3

typedef pair<int, int> P;



struct State {

    int g, h;

    string state;

    P blank;

    string path;

    bool operator<(const State &a) const {

        return g + h > a.g + a.h;

    }

};



int d[5] = {-1, 0, 1, 0, -1};

string r[4] = {"D", "R", "U", "L"};

string ans_str = "";

int ans[N][N], puzzle0[N][N], puzzle1[N][N];

set<string> s;

priority_queue<State> next_state;

string path;



bool range(int y, int x) {return 0 <= y && y < N && 0 <= x && x < N;}



int h2_dfs(int boundary, State state, int from) {

    int find = -1;

    s.insert(state.state); // visited



    P blank = state.blank;

    rep(i, 4) {

        if (from == (i + 2) % 4) continue;

        int y = d[i] + blank.first, x = d[i + 1] + blank.second; // next blank position

        if (range(y, x)) { // can be replaced

            string tmp = state.state; // next state (string)

            int p = blank.first * N + blank.second, q = y * N + x;

            if (N < 4) swap(tmp[p], tmp[q]);

            else swap(tmp[2 * p], tmp[2 * q]), swap(tmp[2 * p + 1], tmp[2 * q + 1]);



            int num;

            if (N < 4) num = state.state[q] - '1';

            else num = stoi(state.state.substr(2 * q, 2)) - 1;

            // calcurate manhattan distance

            int manhattan = state.h - ((abs(num / N - y) + abs(num % N - x)))

            + (abs(num / N - blank.first) + abs(num % N - blank.second));



            if (manhattan == 0) { // answer

                find = state.g + 1;

                path = state.path + r[i];

                break;

            }



            if (state.g + 1 + manhattan > boundary) continue; // estimate value is over boundary

            find = h2_dfs(boundary, State{state.g + 1, manhattan, tmp, P(y, x), state.path + r[i]}, i);

            if (find != -1) break;

        }

    }

    return find;

}



int ids_h2(string state, int manhattan, P blank) {

    int i = manhattan, find = -1;

    while(find == -1 && i < 81) {

        s.clear();

        find = h2_dfs(i, State{0, manhattan, state, blank, ""}, -1);

        i++;

    }

    return find;

}



int main(){

    // create answer's numbers

    iota(ans[0], ans[0] + N * N, 1);

    ans[N - 1][N - 1] = 0;

    // create number

    iota(puzzle0[0], puzzle0[0] + N * N, 0);

    rep(i, N)rep(j, N) cin >> puzzle0[i][j];



    string state = "";

    P blank;

    int manhattan = 0, wrong_place = 0;

    rep(i, N)rep(j, N) {

        state += to_string(puzzle0[i][j]);

        ans_str += to_string(ans[i][j]);



        if(puzzle0[i][j] == 0) blank = P(i, j);

        else {

            int num = puzzle0[i][j] - 1;

            manhattan += (abs(num / N - i) + abs(num % N - j));

            if (puzzle0[i][j] != ans[i][j]) wrong_place++;

        }

    }



    if (manhattan == 0) { // the answer

        cout << 0 << endl;

    } else {

        int steps;

        next_state.push(State{0, wrong_place, state, blank, ""});

        steps = ids_h2(state, manhattan, blank);

        cout << steps << endl;

    }

    return 0;

}