#include<bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;
using ull = unsigned long long;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;

#define fi first
#define se second
#define pb push_back
#define pf push_front
#define mp make_pair
#define ins insert
#define btpc __builtin_popcount
#define btclz __builtin_clz

#define sz(x) (int)(x.size());
#define all(x) x.begin(), x.end()
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};

template<class X, class Y>
    bool minimize(X &x, const Y &y) {
        if (x > y)
        {
            x = y;
            return true;
        }
        return false;
    }
template<class X, class Y>
    bool maximize(X &x, const Y &y) {
        if (x < y)
        {
            x = y;
            return true;
        }
        return false;
    }

const int MOD = 1e9 + 7; //998244353

template<class X, class Y>
    void add(X &x, const Y &y) {
        x = (x + y);
        if(x >= MOD) x -= MOD;
    }

template<class X, class Y>
    void sub(X &x, const Y &y) {
        x = (x - y);
        if(x < 0) x += MOD;
    }

/* Author : Le Ngoc Bao Anh, 11A5, LQD High School for Gifted Student*/

const ll INF = 1e9;
const int N = 100 + 10;

struct Dinitz {
    struct Edges {
        int u, v;
        ll cap;

        Edges() : u(), v(), cap() {}
        Edges(int _u, int _v, ll _cap) : u(_u), v(_v), cap(_cap) {}
    };

    vector<vector<int>> g;
    vector<Edges> ed;
    vector<int> dist;
    vector<int> id;
    int S, T;
    int n;

    Dinitz() : ed(), n(), S(), T() {}
    Dinitz(int _n, int _S, int _T) {
        n = _n; S = _S; T = _T;
        g.resize(n);
        dist.resize(n);
        id.resize(n);
        for(int i = 0; i < n; i++) g[i].clear();
        ed = vector<Edges>();
    }

    void addEdge(int u, int v, ll cap) {
        g[u].pb((int)ed.size());
        ed.pb(Edges(u, v, cap));
        g[v].pb((int)ed.size());
        ed.pb(Edges(v, u, 0));
    }

    bool bfs() {
        for(int i = 0; i < n; i++) dist[i] = n + 5;
        queue<int> q;
        q.push(S); dist[S] = 0;
        while(!q.empty()) {
            int u = q.front(); q.pop();
            for(int i : g[u]) {
                Edges e = ed[i];
                if(!e.cap) continue;
                if(dist[e.v] <= dist[u] + 1) continue;
                dist[e.v] = dist[u] + 1;
                q.push(e.v);
            }
        }

        return dist[T] < n + 5;
    }

    ll dfs(int u, ll flow) {
        if(u == T || flow == 0) return flow;

        ll ans = 0;
        for(int &i = id[u]; i < (int)g[u].size(); i++) {
            Edges e = ed[g[u][i]];
            if(!e.cap) continue;
            if(dist[e.v] != dist[u] + 1) continue;
            ll f = dfs(e.v, min(flow, e.cap));
            flow -= f;
            ans += f;
            ed[g[u][i]].cap -= f;
            ed[g[u][i] ^ 1].cap += f;
            if(flow == 0) return ans;
        }

        return ans;
    }

    ll Flow() {
        ll ans = 0;
        while(bfs()) {
            for(int i = 0; i < n; i++) id[i] = 0;
            ans += dfs(S, INF * INF);
        }

        return ans;
    }

    bool check() {
        for(int i = 0; i < ed.size(); i++) {
            if(ed[i].u < S && ed[i].v < S) continue;
            int u = ed[i].u, v = ed[i].v;
            if(v == S) continue;
            if(u == T) continue;
            if(ed[i].cap) {
                return false;
            }
        }

        return true;
    };
};

char a[N][N];
int ln[N][N][N];
int hn[N][N][N];
int lm[N][N][N];
int hm[N][N][N];

void solve() {
    int n, m;
    cin >> n >> m;
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= m; j++) {
            cin >> a[i][j];
        }
    }

    int v = max(n, m);
    for(int i = 0; i <= m; i++) {
        for(int j = 0; j <= m; j++) {
            if(i + j > m) break;
            int r = m - i - j;
            for(int x = 0; x <= v; x++) {
                ln[i][j][x] = INF;
                hn[i][j][x] = 0;
                for(int d = 0; d <= r; d++) {
                    if(abs(i + d - (j + (r - d))) <= x) {
                        minimize(ln[i][j][x], d);
                        maximize(hn[i][j][x], d);
                    }
                }
            }
        }
    }

    for(int i = 0; i <= n; i++) {
        for(int j = 0; j <= n; j++) {
            if(i + j > n) break;
            int r = n - i - j;
            for(int x = 0; x <= v; x++) {
                lm[i][j][x] = INF;
                hm[i][j][x] = 0;
                for(int d = 0; d <= r; d++) {
                    if(abs(i + d - (j + (r - d))) <= x) {
                        minimize(lm[i][j][x], d);
                        maximize(hm[i][j][x], d);
                    }
                }
            }
        }
    }

    auto ok = [&](int x) -> int {
        int S = n + m + 1, T = n + m + 2;
        int _S = n + m + 3, _T = n + m + 4;
        Dinitz G = Dinitz(n + m + 6, _S, _T);

        for(int i = 1; i <= n; i++) {
            int one = 0, zero = 0;
            for(int j = 1; j <= m; j++) {
                one += (a[i][j] == '1');
                zero += (a[i][j] == '0');
            }

            int lo = ln[one][zero][x];
            int hi = hn[one][zero][x];

            if(lo > hi) return false;
            //edge S -> i, d = lo, c = hi
            G.addEdge(_S, i, lo);
            G.addEdge(S, _T, lo);
            G.addEdge(S, i, hi - lo);
        }

        for(int j = 1; j <= m; j++) {
            int one = 0, zero = 0;
            for(int i = 1; i <= n; i++) {
                one += (a[i][j] == '1');
                zero += (a[i][j] == '0');
            }

            int lo = lm[one][zero][x];
            int hi = hm[one][zero][x];

            if(lo > hi) return false;
            //edge j -> T, d = lo, c = hi
            G.addEdge(_S, T, lo);
            G.addEdge(j + n, _T, lo);
            G.addEdge(j + n, T, hi - lo);
        }

        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= m; j++) {
                if(a[i][j] == '*') G.addEdge(i, j + n, 1);
            }
        }


        G.addEdge(T, S, INF);
        G.Flow();

        return G.check();
    };
    int L = 0, R = max(n, m), ans = 100;
    while(L <= R) {
        int mid = (L + R) >> 1;
        if(ok(mid)) {
            ans = mid;
            R = mid - 1;
        } else L = mid + 1;
    }

    cout << ans;
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #else
    //online
    #endif

    int tc = 1, ddd = 0;
    // cin >> tc;
    while(tc--) {
        //ddd++;
        //cout << "Case #" << ddd << ": ";
        solve();
    }
}