#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
const int D[]={0,-1,0,1,0};

struct P{
    int d, y, x, pp, p;
};

int M[101][101], vis[101][101][10][10];

bool isKado(int a, int b, int c){
    return (a != b&&b != c&&c != a) && (b == max({a, b, c}) || b == min({a, b, c}));
}

int main(){
    int W, H; cin >> W >> H;
    rep(y, H)rep(x, W)scanf("%d", &M[y][x]);

    queue<P> Q;
    Q.push(P{0,0,0,0,0});
    while(sz(Q)){
        P p = Q.front(); Q.pop();
        if(p.y < 0 || p.x < 0 || p.y >= H || p.x >= W || (p.pp && !isKado(p.pp, p.p, M[p.y][p.x])))continue;
        if(vis[p.y][p.x][p.pp][p.p]++)continue;
        if(p.y == H - 1 && p.x == W - 1){
            cout << p.d << endl;
            return 0;
        }
        rep(i, 4){
            Q.push(P{p.d + 1,p.y + D[i],p.x + D[i + 1],p.p,M[p.y][p.x]});
        }
    }

    puts("-1");
}