#include <algorithm>
#include <bitset>
#include <cmath>
#include <complex>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <regex>
#include <set>
#include <stack>
#include <string>
#include <vector>

const int MOD = 1e9 + 7;
const int iINF = 2147483647 / 2;
const long long int llINF = 9223372036854775807 / 2;

using namespace std;
using ll = long long int;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using vvvl = vector<vector<vector<ll>>>;

typedef pair<ll, ll> pll;
bool paircomp(const pll &a, const pll &b) {
  if (a.first == b.first)
    return a.second < b.second;
  return a.first < b.first;
}

#define REP(i, n) for (ll i = 0; i < (n); i++)
#define RREP(i, n) for (ll i = (n)-1; i >= 0; i--)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define AUTO(i, m) for (auto &i : m)
#define ALL(a) (a).begin(), (a).end()
#define MAX(vec) *std::max_element(vec.begin(), vec.end())
#define MIN(vec) *std::min_element(vec.begin(), vec.end())
#define ARGMAX(vec)                                                            \
  std::distance(vec.begin(), std::max_element(vec.begin(), vec.end()))
#define ARGMIN(vec)                                                            \
  std::distance(vec.begin(), std::min_element(vec.begin(), vec.end()))
#define REV(T) greater<T>()
#define PQ(T) priority_queue<T, vector<T>, greater<T>>
#define VVL(a, b, c) vector<vector<ll>>(a, vector<ll>(b, c))
#define VV(T, a, b, c) vector<vector<T>>(a, vector<T>(b, c))
#define VVVL(a, b, c, d)                                                       \
  vector<vector<vector<ll>>>(a, vector<vector<ll>>(b, vector<ll>(c, d)))
#define VVV(T, a, b, c, d)                                                     \
  vector<vector<vector<T>>>(a, vector<vector<T>>(b, vector<T>(c, d)))
#define SP(a) setprecision(a)
#define SQRT(a) sqrt((long double)(a))
#define DPOW(a, b) pow((long double)(a), (long double)(b))
#define UNIQUE(vec)                                                            \
  do {                                                                         \
    sort(ALL((vec)));                                                          \
    (vec).erase(std::unique(ALL((vec))), (vec).end());                         \
  } while (0)

ll POW(ll n, ll m) {
  if (m == 0) {
    return 1;
  } else if (m % 2 == 0) {
    ll tmp = POW(n, m / 2);
    return (tmp * tmp);
  } else {
    return (n * POW(n, m - 1));
  }
}

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ll H, W;
  cin >> H >> W;
  vector<string> P(H);
  REP(i, H) cin >> P[i];
  vvvl DP = VVVL(H, W, 2, llINF);
  queue<tuple<ll, ll, ll, ll>> que;
  que.push(make_tuple(0, 0, 0, 0));

  ll ans = llINF;

  while (!que.empty()) {
    auto pos = que.front();
    que.pop();
    ll count = get<2>(pos);
    ll color = get<3>(pos);
    if (get<0>(pos) >= H || get<1>(pos) >= W)
      continue;
    if (P[get<0>(pos)][get<1>(pos)] == '#' && color == 0) {
      count++;
      color = 1;
    } else if (P[get<0>(pos)][get<1>(pos)] == '.' && color == 1) {
      count++;
      color = 0;
    }
    if (DP[get<0>(pos)][get<1>(pos)][color] <= count)
      continue;
    DP[get<0>(pos)][get<1>(pos)][color] = count;
    if (get<0>(pos) == H - 1 && get<1>(pos) == W - 1) {
      ans = min(ans, count);
    } else {
      que.push(make_tuple(get<0>(pos) + 1, get<1>(pos), count, color));
      que.push(make_tuple(get<0>(pos), get<1>(pos) + 1, count, color));
    }
  }
  cout << (ans + 1) / 2 << endl;

  return 0;
}


Measured memory_bytes: 1024