#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cmath>
#include <queue>
#include <stack>

#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
typedef long long ll;

using namespace std;


int inputValue(){
    int a;
    cin >> a;
    return a;
};

void inputArray(int * p, int a){
    rep(i, a){
        cin >> p[i];
    }
};

void inputVector(vector<int> * p, int a){
    rep(i, a){
        int input;
        cin >> input;
        p -> push_back(input);
    }
}

template <typename T>
void output(T a, int precision) {
    if(precision > 0){
        cout << setprecision(precision)  << a << "\n";
    }
    else{
        cout << a << "\n";
    }
}

bool isKado(int a, int b, int c){
    
    if ((c < a && a < b) || (b < a && a < c) || (a < c && c < b) || (b < c && c < a)) {
        return true;
    }
    else{
        return false;
    }
}

int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};

int main(int argc, const char * argv[]) {
    
    // source code
    int W = inputValue(); // 2以上
    int H = inputValue(); // 2以上
    vector<vector<int> > M(W, vector<int>(H));
    vector<vector<int> > C(W, vector<int>(H)); //最短
    //vector<vector<bool> > V(W, vector<bool>(H)); //通ったか
    // bool V[200][200];
    
    rep(i, W){
        rep(j, H){
            M[i][j] = inputValue();
            // V[i][j] = false;
            C[i][j] = 0;
        }
    }
    
    queue<pair<pair<int, int>, int>> q;
    if (H >= 3) {
        if (isKado(M[0][0], M[0][1], M[0][2])) {
            q.push(make_pair(make_pair(0, 2), M[0][1]));
            C[0][2] = 2;
        }
    }
    if (isKado(M[0][0], M[0][1], M[1][1])) {
        q.push(make_pair(make_pair(1, 1), M[0][1]));
        C[1][1] = 2;
    }
    if (isKado(M[0][0], M[1][0], M[1][1])) {
        q.push(make_pair(make_pair(1, 1), M[1][0]));
        C[1][1] = 2;
    }
    if (W >= 3) {
        if (isKado(M[0][0], M[1][0], M[2][0])) {
            q.push(make_pair(make_pair(2, 0), M[1][0]));
            C[2][0] = 2;
        }
    }
    
    int count = 0;
    
    while (!q.empty() && count < 100000) {
        int x = q.front().first.first;
        int y = q.front().first.second;
        int prevM = q.front().second;
        q.pop();
        // V[x][y] = true;
        
        rep(i, 4){
            int nx = x + dx[i];
            int ny = y + dy[i];
            
            if (nx < 0 || nx >= W || ny < 0 || ny >= H) {
                continue;
            }
            
            if (isKado(prevM, M[x][y], M[nx][ny])) {
                q.push(make_pair(make_pair(nx, ny), M[x][y]));
                C[nx][ny] = max(C[nx][ny], C[x][y] + 1);
            }
            
        }
        count++;
        
    }
    
    output((C[W - 1][H - 1] != 0) ? C[W - 1][H - 1] : -1, 0);
    
    
    
    return 0;
}