#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int dp[105][105][10][10];
constexpr int dx[4] = {1, 0, -1, 0};
constexpr int dy[4] = {0, 1, 0, -1};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int H, W;
    cin >> W >> H;
    vector<vector<int>> M(H, vector<int>(W));
    for(int i = 0; i < H; ++i){
        for(int j = 0; j < W; ++j){
            cin >> M[i][j];
        }
    }

    for(int i = 0; i < H; ++i){
        for(int j = 0; j < W; ++j){
            for(int k = 0; k < 10; ++k){
                for(int l = 0; l < 10; ++l){
                    dp[i][j][k][l] = INF;
                }
            }
        }
    }

    using node = tuple<int, int, int, int>;
    queue<node> que;
    if(M[0][0] != M[0][1]){
        dp[0][1][M[0][1]][M[0][0]] = 1;
        que.emplace(0, 1, M[0][1], M[0][0]);
    }
    if(M[0][0] != M[1][0]){
        dp[1][0][M[1][0]][M[0][0]] = 1;
        que.emplace(1, 0, M[1][0], M[0][0]);
    }
    
    while(!que.empty()){
        auto [x, y, p, q] = que.front();
        que.pop();
        for(int i = 0; i < 4; ++i){
            int nx = x + dx[i], ny = y + dy[i];
            if(nx < 0 || nx >= H || ny < 0 || ny >= W)  continue;
            if(M[nx][ny] == p || M[nx][ny] == q)    continue;
            vector<int> a(3);
            a[0] = p; a[1] = q; a[2] = M[nx][ny];
            sort(begin(a), end(a));
            if(a[1] == q || a[1] == M[nx][ny]){
                if(chmin(dp[nx][ny][M[nx][ny]][p], dp[x][y][p][q] + 1)){
                    que.emplace(nx, ny, M[nx][ny], p);
                }
            }
        }
    }

    int ans = INF;
    for(int i = 0; i < 10; ++i){
        for(int j = 0; j < 10; ++j){
            chmin(ans, dp[H - 1][W - 1][i][j]);
        }
    }
    if(ans == INF)  ans = -1;
    cout << ans << endl;

    return 0;
}