#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define ITER(c)             __typeof__((c).begin())
#define FOREACH(it, c)      for (ITER(c) it=(c).begin(); it != (c).end(); ++it)
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))
#define RREP(i, n)          for(int(i)=(n)-1;(i)>=0;--(i))
const int MOD = (int)1e9+7;

const int INF = (1<<29);
int m[111][111];
int step[111][111][111][111];
const int dir[][2] = {{1,0},{0,1},{-1,0},{0,-1}};

struct V {
    int x1,y1,x2,y2;
    V(int x1,int y1,int x2,int y2) :
        x1(x1),y1(y1),x2(x2),y2(y2){;}
};

bool isKadomatsuSequence(int a, int b, int c){
    if(a == b || a == c || b == c) return false;
    if(b == max(max(a,c),b)) return true;
    if(b == min(min(a,c),b)) return true;
    return false;
}

int main(){
    int W,H; cin >> W >> H;
    REP(y,H) REP(x,W){
        cin >> m[y][x];
    }
    REP(y,H) REP(x,W) REP(y2,H) REP(x2,W)
        step[y2][x2][y][x] = INF;

    deque<V> q;
    q.push_back(V(-1,-1,0,0));

    while(!q.empty()){
        auto v = q.front(); q.pop_front();
        if(v.y2 == H-1 && v.x2 == W-1){
            cout << step[v.y1][v.x1][v.y2][v.x2] << endl;
            return 0;
        }
        int c = 0;
        if(v.x1 >= 0  && v.y1 >= 0){
            c = step[v.y1][v.x1][v.y2][v.x2] + 1;
        } else {
            c = 1;
        }
        REP(d,4){
            int mx = v.x2 + dir[d][0];
            int my = v.y2 + dir[d][1];
            if(mx < 0 || my < 0 || mx >= W || my >= H) continue;

            if(step[v.y2][v.x2][my][mx] <= c) continue;
            if(v.x1 >= 0  && v.y1 >= 0 &&
                !isKadomatsuSequence(m[v.y1][v.x1], m[v.y2][v.x2], m[my][mx])) continue;
            step[v.y2][v.x2][my][mx] = c;
            q.push_back(V(v.x2,v.y2,mx,my));
        }
    }
    cout << -1 << endl;
}