# include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
const double pi = acos(-1);
template<class T>constexpr T inf() { return ::std::numeric_limits<T>::max(); }
template<class T>constexpr T hinf() { return inf<T>() / 2; }
template <typename T_char>T_char TL(T_char cX) { return tolower(cX); }
template <typename T_char>T_char TU(T_char cX) { return toupper(cX); }
template<class T> bool chmin(T& a,T b) { if(a > b){a = b; return true;} return false; }
template<class T> bool chmax(T& a,T b) { if(a < b){a = b; return true;} return false; }
template<class T> bool is_sqare(T a) { if(floor(sqrt(a)) * floor(sqrt(a)) == a){ return true; }return false; }
int popcnt(unsigned long long n) { int cnt = 0; for (int i = 0; i < 64; i++)if ((n >> i) & 1)cnt++; return cnt; }
int d_sum(ll n) { int ret = 0; while (n > 0) { ret += n % 10; n /= 10; }return ret; }
int d_cnt(ll n) { int ret = 0; while (n > 0) { ret++; n /= 10; }return ret; }
ll gcd(ll a, ll b) { if (b == 0)return a; return gcd(b, a%b); };
ll lcm(ll a, ll b) { ll g = gcd(a, b); return a / g*b; };
template<class T> using dijk = priority_queue<T, vector<T>, greater<T>>;
# define all(qpqpq)           (qpqpq).begin(),(qpqpq).end()
# define UNIQUE(wpwpw)        (wpwpw).erase(unique(all((wpwpw))),(wpwpw).end())
# define LOWER(epepe)         transform(all((epepe)),(epepe).begin(),TL<char>)
# define UPPER(rprpr)         transform(all((rprpr)),(rprpr).begin(),TU<char>)
# define rep(i,upupu)         for(ll i = 0, i##_len = (upupu);(i) < (i##_len);(i)++)
# define reps(i,opopo)        for(ll i = 1, i##_len = (opopo);(i) <= (i##_len);(i)++)
# define len(x)                ((ll)(x).size())
# define bit(n)               (1LL << (n))
# define pb push_back
# define exists(c, e)         ((c).find(e) != (c).end())
#ifdef LOCAL
#  include "_debug_print.hpp"
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif

struct INIT{
	INIT(){
		std::ios::sync_with_stdio(false);
		std::cin.tie(0);
		cout << fixed << setprecision(20);
	}
}INIT;

void solve(){
	int h, w;
	cin >> h >> w;
	vector<vector<int>> a(h, vector(w, 0));
	rep(i, h)rep(j, w)cin >> a[i][j];
	vector col(h, vector(w, -1));
	col[0][0] = 1;
	col[h-1][w-1] = 0;
	vector<dijk<pair<int, pair<int, int>>>> pq(2);
	pq[0].push({a[h-2][w-1], {h-2, w-1}});
	pq[0].push({a[h-1][w-2], {h-1, w-2}});
	pq[1].push({a[0][1], {0, 1}});
	pq[1].push({a[1][0], {1, 0}});
	int ans = 1;

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

	auto within = [&](int y, int x) -> bool {
		return 0 <= y && y < h && 0 <= x && x < w;
	};

	while(not pq[ans%2].empty()){
		auto [_, yx] = pq[ans%2].top();
		pq[ans%2].pop();
		auto [y, x] = yx;
		if(col[y][x] != -1)continue;
		col[y][x] = ans%2;
		rep(dir, 4){
			int ny = y+dy[dir];
			int nx = x+dx[dir];
			if(not within(ny, nx))continue;
			if(col[ny][nx] != col[y][x] && col[ny][nx] != -1){
				cout << ans << endl;
				return;
			}
			pq[ans%2].push({a[ny][nx], {ny, nx}});
		}
		ans++;
	}
}

int main(){
    int t = 1;
    //cin >> t;
    while(t--)solve();
}