#include <stdio.h>
 #include <bits/stdc++.h>






using namespace std;




template<class T, size_t... I>
void print_tuple(ostream& s, T const& a, index_sequence<I...>){
  using swallow = int[];
  (void)swallow{0, (void(s << (I == 0? "" : ", ") << get<I>(a)), 0)...};
}

template<class T>
ostream& print_collection(ostream& s, T const& a);
template<class... A>
ostream& operator<<(ostream& s, tuple<A...> const& a);
template<class A, class B>
ostream& operator<<(ostream& s, pair<A, B> const& a);

template<class T, size_t I>
ostream& operator<<(ostream& s, array<T, I> const& a) { return print_collection(s, a); }
template<class T>
ostream& operator<<(ostream& s, vector<T> const& a) { return print_collection(s, a); }
template<class T, class U>
ostream& operator<<(ostream& s, multimap<T, U> const& a) { return print_collection(s, a); }
template<class T>
ostream& operator<<(ostream& s, multiset<T> const& a) { return print_collection(s, a); }
template<class T, class U>
ostream& operator<<(ostream& s, map<T, U> const& a) { return print_collection(s, a); }
template<class T>
ostream& operator<<(ostream& s, set<T> const& a) { return print_collection(s, a); }

template<class T>
ostream& print_collection(ostream& s, T const& a){
  s << '[';
  for(auto it = begin(a); it != end(a); ++it){
    s << *it;
    if(it != prev(end(a))) s << " ";
  }
  return s << ']';
}

template<class... A>
ostream& operator<<(ostream& s, tuple<A...> const& a){
  s << '(';
  print_tuple(s, a, index_sequence_for<A...>{});
  return s << ')';
}

template<class A, class B>
ostream& operator<<(ostream& s, pair<A, B> const& a){
  return s << "(" << get<0>(a) << ", " << get<1>(a) << ")";
}







using li = long long int;
using lu = long long unsigned;
using ld = long double;


using pii = tuple<li, li>;
using piii = tuple<li, li, li>;
using piiii = tuple<li, li, li, li>;
using vi = vector<li>;
using vii = vector<pii>;
using viii = vector<piii>;
using vvi = vector<vi>;
using vvii = vector<vii>;
using vviii = vector<viii>;

template<class T>
using min_queue = priority_queue<T, vector<T>, greater<T> >;
template<class T>
using max_queue = priority_queue<T>;

struct empty_t {};
namespace tuple_access {

  struct xx_t {} xx;
  struct yy_t {} yy;
  struct zz_t {} zz;
  struct ww_t {} ww;

  template<class T>
  typename tuple_element<0,T>::type& operator^(T& v, xx_t) { return get<0>(v); }
  template<class T>
  typename tuple_element<0,T>::type const& operator^(T const& v, xx_t) { return get<0>(v); }
  template<class T>
  typename tuple_element<0,T>::type&& operator^(T&& v, xx_t) { return get<0>(v); }

  template<class T>
  typename tuple_element<1,T>::type& operator^(T& v, yy_t) { return get<1>(v); }
  template<class T>
  typename tuple_element<1,T>::type const& operator^(T const& v, yy_t) { return get<1>(v); }
  template<class T>
  typename tuple_element<1,T>::type&& operator^(T&& v, yy_t) { return get<1>(v); }

  template<class T>
  typename tuple_element<2,T>::type& operator^(T& v, zz_t) { return get<2>(v); }
  template<class T>
  typename tuple_element<2,T>::type const& operator^(T const& v, zz_t) { return get<2>(v); }
  template<class T>
  typename tuple_element<2,T>::type&& operator^(T&& v, zz_t) { return get<2>(v); }

  template<class T>
  typename tuple_element<3,T>::type& operator^(T& v, ww_t) { return get<3>(v); }
  template<class T>
  typename tuple_element<3,T>::type const& operator^(T const& v, ww_t) { return get<3>(v); }
  template<class T>
  typename tuple_element<3,T>::type&& operator^(T&& v, ww_t) { return get<3>(v); }
}
using namespace tuple_access;


int ilog2(int x){ return 31 - __builtin_clz(x); }

template <class T>
struct identity : std::unary_function <T, T> {
  T operator() (const T& x) const {return x;}
};

template<class T>
T& smin(T& x, T const& y) { x = min(x,y); return x; }

template <class T>
T& smax(T& x, T const& y) { x = max(x, y); return x; }


template<typename T>
T isqrt(T const&x){
  static_assert(is_integral<T>::value, "is_integral<T>::value");
  assert(x>=T(0));
  T ret = static_cast<T>(sqrtl(x));
  while(ret>0 && ret*ret>x) --ret;
  while(x-ret*ret>2*ret) ++ret;
  return ret;
}

template<typename T>
T icbrt(T const&x) {
  static_assert(is_integral<T>::value, "is_integral<T>::value");
  assert(x>=T(0));
  T ret = static_cast<T>(cbrt(x));
  while(ret>0 && ret*ret*ret>x) --ret;
  while(x-ret*ret*ret>3*ret*(ret+1)) ++ret;
  return ret;
}

const int N = 200;
int A[N][N];

int dp[N+1][N+1];

int main(){
  ios::sync_with_stdio(0); cin.tie(0);
  int n,m; cin>>n>>m;
  for(li i = 0; i < (li)(n); ++i) for(li j = 0; j < (li)(m); ++j) {
    char c; cin>>c;
    A[i][j] = (c=='#');
  }
  for(li i = 0; i < (li)(n); ++i) for(li j = 0; j < (li)(m); ++j) dp[i][j] = 1e9;
  dp[0][0] = !!A[0][0];
  for(li i = 0; i < (li)(n); ++i) for(li j = 0; j < (li)(m); ++j) {
    if(i+1<n){
      dp[i+1][j] = min(dp[i+1][j], dp[i][j]+!!(!A[i][j] && A[i+1][j]));
    }
    if(j+1<m){
      dp[i][j+1] = min(dp[i][j+1], dp[i][j]+!!(!A[i][j] && A[i][j+1]));
    }
  }
  cout << dp[n-1][m-1] << endl;
  return 0;
}


Measured memory_bytes: 384