#include <bits/stdc++.h>
using namespace std;

int main(){
    int h,w;cin>>h>>w;
    vector<vector<long long>> a(h,vector<long long>(w));
    unordered_map<long long,pair<int,int>> mp;
    for(int i=0;i<h;i++)for(int j=0;j<w;j++){
        cin>>a[i][j];
        mp[a[i][j]]={i,j};
    }
    unordered_set<long long> st0,st1;
    priority_queue<long long,vector<long long>,greater<long long>> pq1,pq0;
    vector<int> dx={1,0,-1,0},dy={0,1,0,-1};
    int idx=1;
    pq1.push(a[0][0]);
    pq0.push(a[h-1][w-1]);
    while(!pq1.empty()||!pq0.empty()){
        if((idx&1)==0){
            idx++;
            while(!pq0.empty()&&st0.count(pq0.top()))pq0.pop();
            if(pq0.empty()){
                continue;
            }
            auto x=pq0.top();pq0.pop();
            st0.insert(x);
            for(int i=0;i<4;i++){
                if(mp[x].first+dx[i]<0||mp[x].first+dx[i]>=h)continue;
                if(mp[x].second+dy[i]<0||mp[x].second+dy[i]>=w)continue;
                if(st0.count(a[mp[x].first+dx[i]][mp[x].second+dy[i]]))continue;
                if(st1.count(a[mp[x].first+dx[i]][mp[x].second+dy[i]])){
                    cout<<idx-3<<"\n";
                    return 0;
                }
                pq0.push(a[mp[x].first+dx[i]][mp[x].second+dy[i]]);
            }
        }else{
            idx++;
            while(!pq1.empty()&&st1.count(pq1.top()))pq1.pop();
            if(pq1.empty()){
                continue;
            }
            auto x=pq1.top();pq1.pop();
            st1.insert(x);
            for(int i=0;i<4;i++){
                if(mp[x].first+dx[i]<0||mp[x].first+dx[i]>=h)continue;
                if(mp[x].second+dy[i]<0||mp[x].second+dy[i]>=w)continue;
                if(st1.count(a[mp[x].first+dx[i]][mp[x].second+dy[i]]))continue;
                if(st0.count(a[mp[x].first+dx[i]][mp[x].second+dy[i]])){
                    cout<<idx-3<<"\n";
                    return 0;
                }
                pq1.push(a[mp[x].first+dx[i]][mp[x].second+dy[i]]);
            }
        }
    }
}