//the AStar algorithm

#include<stdio.h>
#include<string.h>
#include<malloc.h>
#define ALL 362880

int fac[9] = {1, 1, 2, 6, 24, 120, 720, 5040, 40320};

//0 for not appeared, 1 for appeared in future, 2 for passed
char flag[ALL];

//  if a num 's position of the target state is  row & cur state  col ,
// then the "distance" --h  is table[row][col]
char table[9][9] = {
    0, 1, 2, 1, 2, 3, 2, 3, 4,
    1, 0, 1, 2, 1, 2, 3, 2, 3,
    2, 1, 0, 3, 2, 1, 4, 3, 2,
    1, 2, 3, 0, 1, 2, 1, 2, 3,
    2, 1, 2, 1, 0, 1, 2, 1, 2,
    3, 2, 1, 2, 1, 0, 3, 2, 1,
    2, 3, 4, 1, 2, 3, 0, 1, 2,
    3, 2, 3, 2, 1, 2, 1, 0, 1,
    4, 3, 2, 3, 2, 1, 2, 1, 0,
};
class node
{
public:
    //f = g + h is the evaluation func
    int g;    //steps
    int h;   // the evaluated distance
    int zero;
    char s[9];
    char last;
};
node states[ALL];
node *head = states;
node *tail;

//notice how to get cantor func
int cantor(char *s)
{
    int sum = 1;

    for (int i = 0; i < 9; ++i) {
        int n = 0;

        for (int j = i + 1; j < 9 ; ++j) {
            if (s[j] < s[i]) {
                ++ n;
            }
        }

        sum += n * fac[8 - i];
    }

    return sum;
}
void init(char *s)
{
    memset(states, 0, sizeof(node)*ALL);
    memset(flag, 0, sizeof(flag));
    flag[cantor(s)] = 1;
    tail = head + 1;
    head -> g = 0;
    head -> h = 0;

    for (int i = 0; i < 9; ++i) {
        head->h += table[8 - (s[i] - '0')][i];
    }

    head ->last = -1;

    for (int i = 0; i < 9; ++i) {
        if (s[i] == '0') {
            head -> zero = i;
        }

        head->s[i] = s[i];
    }
}

// arrange a new state
void putIn(node *n)
{
    int f = n -> g + n -> h;
    node *tmp = head;

    for (; tmp < tail; ++tmp) {
        if (f < tmp -> g + tmp -> h)
            break;
    }

    node *p ;

    for (p = tail; p > tmp; --p) {
        *p = *(p - 1);
    }

    *p = *n;
    ++tail;
}

//choose the smaller f of a state
void updt(node *n)
{
    node *tmp ;

    for (tmp = head; tmp < tail ; ++tmp) {
        if (strcmp(tmp -> s, n -> s) == 0) {
            tmp -> g = n -> g;
            tmp -> last = n-> last;
            break;
        }
    }

    node *mid = new node();  //new  return a pointer ! Remember!
    node * i;

    for (i = tmp; i > head && (i->g + i->h < (i - 1)->g + (i - 1)->h); --i) {
        *mid = *i;
        *i = * (i - 1);
        *(i - 1) = *mid;
    }

    if (i > head && i->g + i->h < (i - 1)->g + (i - 1)->h && i->g < (i - 1)->g) {
        *mid = *i;
        *i = * (i - 1);
        *(i - 1) = *mid;
    }

    delete mid;
}

int move()
{
    while (head != tail) {
        node *tmp = head;
        ++head;

        if (cantor(tmp->s) == ALL)
            return tmp -> g;

        flag[cantor(tmp -> s)] = 2;
        int dir[4] = {-3, 1, 3, -1};

        if (tmp -> last != -1)
            dir[tmp-> last] = 0;

        if (tmp -> zero < 3) dir[0] = 0;

        if (tmp -> zero > 5) dir[2] = 0;

        if ((tmp -> zero) % 3 == 0) dir[3] = 0;

        if ((tmp -> zero) % 3 == 2) dir[1] = 0;

        for (int i = 0; i < 4; ++i) {
            if (dir[i] != 0) {
                node *cur = new node();
                *cur = *tmp;
                int p = cur ->zero;
                cur -> zero = p + dir[i];
                cur -> s[p] = cur -> s[p + dir[i]];
                cur -> s[p + dir[i]] = '0';
                int pn = cantor(cur -> s);

                if (flag[pn] != 2) {
                    cur -> g += 1;
                    cur->last = (2 + i) % 4; //һβܷ,ƶ2+i%4
                    int delta = table[8 - cur -> s[p] + '0'][p] + table[8][cur -> zero] \
                                - table[8 - cur -> s[p] + '0'][cur -> zero] - table[8][p];
                    cur -> h += delta;

                    if (flag[pn] == 0) {
                        flag[pn] = 1;
                        putIn(cur);
                    } else  updt(cur);
                } else delete cur;
            }
        }
    }
}
char readChar()
{
    char c = ' ';

    while (c == ' ' || c == '\n')
        c = getchar();

    return c;
}
int main(void)
{
    // char s[10] = "876543210";
    char s[9];

    for (int i = 0 ; i < 9; ++i) {
        s[i] = readChar();
    }

    init(s);
    printf("%d\n", move());
    return 0;
}