#include<bits/stdc++.h>

using namespace std;
typedef unsigned int uint;
typedef long long int ll;
typedef unsigned long long int ull;

#define debugv(v) printf("L%d %s => ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;
#define debugm(m) printf("L%d %s is..\n",__LINE__,#m);for(auto v:m){for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) printf("L%d %s is => ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;
#define debugaa(m,w,h) printf("L%d %s is..\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[x][y]<<" ";}cout<<endl;}
#define ALL(v) (v).begin(),(v).end()
#define BIGINT 0x7FFFFFFF
#define E107 1000000007
void printbit(int u){if(u==0)cout<<0;else{int s=0,k=0;for(;0<u;u>>=1,k++)s=(s<<1)|(u&1);for(;0<k--;s>>=1)cout<<(s&1);}}

#define TIME chrono::system_clock::now()
#define MILLISEC(t) (chrono::duration_cast<chrono::milliseconds>(t).count())

template<typename T1,typename T2>
ostream& operator <<(ostream &o,const pair<T1,T2> p){o<<"("<<p.first<<":"<<p.second<<")";return o;}

int width,height;
int m,n;

map<vector<vector<int>>,int> dp;

void flipx(vector<vector<int>>& field){
    int x,y;
    for (y=0;y<height;y++)
        for (x=0;x<width/2;x++){
            swap(field[y][x],field[y][width-x-1]);
        }
    return;
}
void flipy(vector<vector<int>>& field){
    int x,y;
    for (y=0;y<height/2;y++){
        field[y].swap(field[height-y-1]);
    }
    return;
}

int main(){
    int i,j,k;
    int x,y,a,b;
    
    cin >> height >> width;
    
    vector<vector<int>> first; // cww
    vector<vector<int>> final; // zero
    
    for (y=0;y<height;y++){
        first.emplace_back(width);
        final.emplace_back(width);
        for (x=0;x<width;x++){
            cin >> first[y][x];
        }
    }
    
    // all zero
    
    queue<pair<int,vector<vector<int>>> > q;
    
    q.push(make_pair(1,final));
    dp[final] = 1;
    q.push(make_pair(10001,first));
    dp[first] = 10001;
    
    auto tim = TIME;
    
    while (!q.empty()){
        if (MILLISEC(TIME-tim)>1800) abort();
        pair<int,vector<vector<int>>> p = q.front();
        q.pop();
        
        //if (dp.size()>100000){
        //    cout << dp.size() << endl;return 0;
        //}
        
        if (p.first<10000 && p.second == first){
            cout << (p.first-1) << endl;
            return 0;
        }
        if (p.first>=10000 && p.second == final){
            cout << (p.first-10001) << endl;
            return 0;
        }
        
        for (y=0;y<height;y++){
            for (x=0;x<width;x++){
                vector<vector<int>> tmp = p.second;
                for (i=-1+(x==0);i<=1-(x==width-1);i++){
                    for (j=-1+(y==0);j<=1-(y==height-1);j++){
                        tmp[y+j][x+i]^=1;
                    }
                }
                //vector<vector<int>> tmp2 = tmp;
                bool flg = true;
                for (i=0;i<4;i++){
                    if (i%2==1){
                        flipx(tmp);
                    }
                    if ((i/2)%2==1){
                        flipy(tmp);
                    }
                    
                    if (dp.count(tmp)){
                        flg = false;
                        
                        int &val = dp[tmp];
                        if ((p.first<=10000)^(val<=10000)){
                            //printf("%d %d\n",p.first,val);
                            //cout << "!";
                            cout << (p.first+val-10001) << endl;
                            return 0;
                        }
                    }else{
                        //val = p.first+1;
                    }
                    
                }
                if (flg){
                    
                    dp[tmp] = p.first+1;
                    q.push(make_pair(p.first+1,tmp));
                }
            }
        }
        
        
    }
    
    //cout << dp.size() << endl;
    
    cout << "Impossible" << endl;

    return 0;
}