#include "bits/stdc++.h"
#define Rep(i,n) for(int i=0;i<(int)(n);i++)
#define For(i,n1,n2) for(int i=(int)(n1);i<(int)(n2);i++)
#define REP(i,n) for(ll i=0;i<(ll)(n);i++)
#define RREP(i,n) for(ll i=((ll)(n)-1);i>=0;i--)
#define FOR(i,n1,n2) for(ll i=(ll)(n1);i<(ll)(n2);i++)
#define RFOR(i,n1,n2) for(ll i=((ll)(n1)-1);i>=(ll)(n2);i--)
#define all(a)  (a).begin(),(a).end()
#define SORT(a) sort((a).begin(),(a).end())
#define oorret 0
#define oor(x) [&](){try{x;} catch(const out_of_range& oor){return oorret;} return x;}()
#define IOS std::cin.tie(0),std::ios::sync_with_stdio(false)

namespace idaten{

using namespace std;
using ll = int_fast64_t;
using ull = uint_fast64_t;
using P = std::pair<int64_t, int64_t>;
template<typename T1, typename T2> inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return 1; }return 0; }
template<typename T1, typename T2> inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return 1; }return 0; }
template<class Type>struct is_vector : std::false_type {};
template<class ValueType, class Alloc>struct is_vector<std::vector<ValueType, Alloc>> : std::true_type {};
template <typename T> inline std::ostream& operator << (std::ostream& out, const std::vector<T>& v) {
    if (v.empty())return out;
    constexpr bool is_vector_v = is_vector<T>::value;
    if (is_vector_v)for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? "\n" : "");
    else for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? " " : "");
    return out;
}
inline void put() {}
template<class T> inline void put(const T& first) { std::cout << first << "\n"; }
template<class T, class... N> inline void put(const T& first, const N& ... rest) { std::cout << first << " "; put(rest...); }
inline void putn() {}
template<class T, class... N> inline void putn(const T& first, const N& ... rest) { std::cout << first << "\n"; putn(rest...); }

template<typename T>
struct edge{
    int to;
    T cost;
    edge(int t,T c){
        to = t;
        cost = c;
    }
};

template<typename T>
void dijkstra(int s,vector<vector<edge<T>>>& path,vector<T>& d){
    using pi = pair<T,int>;
    priority_queue<pi,vector<pi>,greater<pi>> q;
    q.push(P(0,s));
    d[s] = 0;
    while(!q.empty()){
        P p = q.top();
        q.pop();
        int v = p.second;
        if(d[v]<p.first)continue;
        REP(i,path[v].size()){
            edge<T> e = path[v][i];
            if(d[e.to]>d[v]+e.cost){
                d[e.to]=d[v]+e.cost;
                q.push(P(d[e.to],e.to));
            }
        }
    }
    return ;
}

void solve(){
    IOS;
    int h,w;
    cin >> h >> w;
    vector<string> s(h);
    REP(i,h){
        cin >> s[i];
    }
    using ei = edge<int>;
    vector<vector<edge<int>>> path(h*w+1);
    int dy[2] = {0,1};
    int dx[2] = {1,0};
    Rep(i,h){
        Rep(j,w){
            REP(k,2){
                int ny = i+dy[k];
                int nx = j+dx[k];
                if(0<=ny&&ny<h&&0<=nx&&nx<w){
                    int now = i*w+j;
                    int nex = ny*w+nx;
                    int cost = 0;
                    if(s[ny][nx]=='#'&&s[i][j]=='.'){
                        cost++;
                    }
                    path[now].push_back(ei(nex,cost));
                }
            }
        }
    }
    int cost = 0;
    if(s[0][0]=='#'){
        cost++;
    }
    path[h*w].push_back(ei(0,cost));
    vector<int> d(h*w+1,INT_MAX/3);
    dijkstra(h*w, path, d);
    put(d[h*w-1]);
}
} // namespace idaten

int main(){
    idaten::solve();
    return 0;
}


Measured memory_bytes: 896