#include<bits/stdc++.h>
using namespace std;
//#include<boost/multiprecision/cpp_int.hpp>
//using boost::multiprecision::cpp_int;

#define int long long
#define cint cpp_int
#define endl "\n"
#define REP(i,a,n) for(int i=a;i<n;++i)
#define REPR(i,a,n) for(int i=a;i>n;--i)
#define RUP(a,b) (((a)+(b)-1)/(b))
#define ALL(v) (v).begin(),(v).end()
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define MOD 1000000007
#define INF LLONG_MAX/2
#define PI acos(-1.0)

typedef long long ll;
typedef pair<int,int> Pii;
typedef tuple<int,int,int> Tiii;
typedef vector<int> Vi;
typedef vector<Vi> VVi;
typedef vector<Pii> VPii;
typedef vector<string> Vs;
typedef priority_queue<int> PQi;

template<class T> inline bool chmax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T> inline bool chmin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
void vout(Vi &v){for(int i=0;i<(v).size();i++) cout<<v[i]<<" ";cout<<endl;}
void vout(Vs &v){for(int i=0;i<(v).size();i++) cout<<v[i]<<" ";cout<<endl;}
void vvout(VVi &v){for(int i=0;i<(v).size();i++) vout(v[i]);}
int gcd(int a,int b){return b?gcd(b,a%b):a;}
int lcm(int a,int b){return a/gcd(a,b)*b;}
int mypow(int x, int n, int m){if(n==0)return 1;if(n%2==0)return mypow(x*x%m,n/2,m);else return x*mypow(x,n-1,m)%m;}
int digit(int k,int i){string s = to_string(k);return s[s.size()-i]-'0';}
void uniq(Vi &v){sort(v.begin(),v.end()); v.erase(unique(v.begin(),v.end()),v.end());} //vectorの同じ要素消す
int ctoi(char c){if(c>='0'&&c<='9'){return c-'0';}return 0;}
int leng(int n){string s=to_string(n); return s.size();} //intの桁数
int digitsum(int n){int ret=0; while(n>0){ret+=n%10;n/=10;}return ret;} //桁和
int lesscount(int x,Vi &a){return lower_bound(a.begin(),a.end(),x)-a.begin();} //vector aにおけるx未満の数の個数
int orlesscount(int x,Vi &a){return upper_bound(a.begin(),a.end(),x)-a.begin();} //vector aにおけるx以下の数の個数
int morecount(int x,Vi &a){return a.size()-orlesscount(x,a);} //vector aにおけるxより大きい数の個数
int ormorecount(int x,Vi &a){return a.size()-lesscount(x,a);} //vector aにおけるx以上の数の個数
int count(int x,Vi &a) {return upper_bound(ALL(a),x)-lower_bound(ALL(a),x);} //vector aにおけるxの個数
Vi accum(Vi &v){Vi ret((v).size()+1);REP(i,0,(v).size()) ret[i+1]=ret[i]+v[i];return ret;}
bool comp(Pii a,Pii b){
    if(a.second != b.second) return a.second<b.second;
    else return a.first<b.first;
}

struct field{
    int H,W;  
    Vs F;
    VVi dist;
    const Vi dx={0,1}, dy={1,0};
    field(int h,int w,Vs s){
        init(h,w,s);
    }
    void init(int h,int w,Vs s){
        H=h; W=w; F=s;
        dist.resize(H);
        REP(i,0,H) dist[i].resize(W);
        REP(i,0,H){
            REP(j,0,W){
                dist[i][j] = INF;
            }
        }
    }
    void update(int h,int w,char c){
        F[h][w]=c;
    }
    bool inside(int h,int w){
    	return (0<=h && h<H && 0<=w && w<W);
    }
    void bfs(int sh=0,int sw=0){
        dist[sh][sw]=0;
        if(F[0][0]=='#') dist[sh][sw]++;
        queue<Pii> q;
        q.push(mp(sh,sw));
        while(!q.empty()){
            int nowh,noww;
            tie(nowh,noww)=q.front();q.pop();
            REP(d,0,dx.size()){
                int newh=nowh+dx[d],neww=noww+dy[d];
                if(inside(newh,neww)){
                    if(F[newh][neww]=='#' && F[nowh][noww]=='.'){
                        if(chmin(dist[newh][neww],dist[nowh][noww]+1)) q.push(mp(newh,neww));
                    }else{
                        if(chmin(dist[newh][neww],dist[nowh][noww])) q.push(mp(newh,neww));
                    }
                }
            }
        }
    }
    int size(){
        int ret=0;
        REP(i,0,H){
            REP(j,0,W){
                if(dist[i][j]>0) ret++;
            }
        }
        return ret;
    }
};


// Generated by 1.1.6 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
signed main(){cin.tie(0);cout.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);
    long long h;
    long long w;
    cin>>h>>w;

    Vs s(h);
    REP(i,0,h) cin>>s[i];

    field F(h,w,s);
    F.bfs();

    cout<<F.dist[h-1][w-1]<<endl;
    return 0;
}


Measured memory_bytes: 384