/*
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*/

///YEAH IM THE BEST I'VE EVER WAS

///SO HAPPY
#include <bits/stdc++.h>

#define popcnt(x) __builtin_popcount(x)

#define fr first

#define sc second

#define m_p make_pair

#define low_bo(a, x) lower_bound(a.begin(), a.end(), x) - a.begin()

#define up_bo(a, x) upper_bound(a.begin(), a.end(), x) - a.begin()

#define unique(a) a.resize(unique(a.begin(), a.end()) - a.begin())

#define popcnt(x) __builtin_popcount(x)

//#include <ext/pb_ds/assoc_container.hpp>

//using namespace __gnu_pbds;

//gp_hash_table<int, int> table;

//#pragma GCC optimize("O3")
//#pragma GCC optimize("Ofast,no-stack-protector")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
//#pragma GCC target("avx,tune=native")
//float __attribute__((aligned(32)))

/*char memory[(int)1e8];

char memorypos;

inline void * operator new(size_t n){
    char * ret = memory + memorypos;
    memorypos += n;
    return (void *)ret;
}

inline void operator delete(void *){}
*/

using namespace std;

typedef long long ll;

typedef unsigned long long ull;

typedef long double ld;

typedef unsigned int uint;

ll sqr(ll x) {
    return x * x;
}

int mysqrt(ll x) {
    int l = 0, r = 1e9 + 1;
    while (r - l > 1) {
        int m = (l + r) / 2;
        if (m * (ll) m <= x)
            l = m;
        else
            r = m;
    }
    return l;
}

#ifdef ONPC
mt19937 rnd(231);
mt19937_64 rndll(231);
#else
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
    mt19937_64 rndll(chrono::high_resolution_clock::now().time_since_epoch().count());
#endif
template<typename T>
T gcd(T a, T b) {
    return a ? gcd(b % a, a) : b;
}

int gcdex(int a, int b, int &x, int &y) {
    if (a == 0) {
        x = 0;
        y = 1;
        return b;
    }
    int x1, y1;
    int ret = gcdex(b % a, a, x1, y1);
    x = y1 - (b / a) * x1;
    y = x1;
    return ret;
}

int Mod = 998244353;

int Bpow(int x, ll y) {
    int ret = 1;
    int w = x;
    while (y) {
        if (y & 1)
            ret = (ret * (ll) w) % Mod;
        w = (w * (ll) w) % Mod;
        y >>= 1;
    }
    return ret;
}

int Bdiv(int x) {
    int a, b;
    gcdex(x, Mod, a, b);
    if (a < 0)
        a += Mod;
    return a;
}

int Bdiv(int x, int y) {
    return (x * (ll) Bpow(y, Mod - 2)) % Mod;
}

inline int ad(int x, int y) {
    return x + y >= Mod ? x + y - Mod : x + y;
}

inline int dif(int x, int y) {
    return x - y < 0 ? x - y + Mod : x - y;
}

inline int mul(int x, int y) {
    return (x * (ll) y) % Mod;
}

int inv(int a) {
    int b = Mod, x = 0, y = 1;
    while (a) {
        int t = b / a;
        b -= a * t;
        x -= t * y;
        swap(a, b);
        swap(x, y);
    }
    if (x < 0)
        x += Mod;
    return x;
}

void setmin(int &x, int y) {
    x = min(x, y);
}

void setmax(int &x, int y) {
    x = max(x, y);
}

void setmin(ll &x, ll y) {
    x = min(x, y);
}

void setmax(ll &x, ll y) {
    x = max(x, y);
}

const ll llinf = 4e18 + 100;

const ld eps = 1e-9;

const int maxn = 2e5 + 10, maxw = 1e6 + 100, inf = 1e9 + 100, sq = 100, LG = 18;

int q[100][100];

int n, m;

int main() {
#ifdef ONPC
    freopen("../a.in", "r", stdin);
    freopen("../a.out", "w", stdout);
#else
    //freopen("a.in", "r", stdin);
    //freopen("a.out", "w", stdout);
#endif // ONPC
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    vector<vector<int> > s(n);
    for (int i = 0; i < n; i++) {
        s[i].resize(m);
        string t;
        cin >> t;
        for (int j = 0; j < m; j++)
            s[i][j] = (t[j] == '#');
    }
    q[0][0] = s[0][0];
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
        if (i + j > 0) {
            int w = inf;
            if (i)
                setmin(w, q[i - 1][j] + s[i][j] * (s[i][j] != s[i - 1][j]));
            if (j)
                setmin(w, q[i][j - 1] + s[i][j] * (s[i][j] != s[i][j - 1]));
            q[i][j] = w;
        }
    cout << q[n - 1][m - 1];
}


Measured memory_bytes: 384