#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define INF (1LL<<57)
#define MV 200001
#define LMV 21
#define ff first
#define ss second
#define pb push_back
#define eb emplace_back
#define emp emplace
#define whoami(x) cerr<<#x<<" "<<x<<"\n";
#define mp make_pair
#define ins insert
#define sz size

void FLASH() {ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);}
void SETF() {cout.ios_base::setf(ios_base::fixed);}
void UNSETF() {cout.ios_base::unsetf(ios_base::fixed);}

typedef long long ll;
typedef long double ld;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef pair<PII, int> PPII;
typedef pair<PLL, ll> PPLL;
typedef map<int, int> MII;

const int MOD = 1000000007;

template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template <typename T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;

struct h_llint {
  static uint64_t splitmix64(uint64_t x) {    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};

struct h_pair{
  size_t operator()(const PLL&x)const{
    return hash<ll>()(((ll)x.ff)^(((ll)x.ss)<<32));
  }
};

typedef map<ll, ll> MLL;
typedef map<PII, int> MPII;
typedef map<PLL, ll> MPLL;
typedef set<int> SI;
typedef set<ll> SL;
//ordered_set = order_of_key(.)
//ordered_set = find_by_order(.)
typedef ordered_set<int> OSI;
typedef ordered_set<ll> OSL;
typedef ordered_multiset<int> MOSI;
typedef ordered_multiset<ll> MOSL;
typedef unordered_map<ll, int, h_llint> UMLI;
typedef unordered_map<ll, ll, h_llint> UMLL;
typedef unordered_map<PLL, int, h_pair> UMPI;
typedef unordered_map<PLL, ll, h_pair> UMPL;

int ar[MV];
ll arr[MV];
string G[101];
int memo[110][110][2];

int xd(int n, int m, bool cv)
{
	if(!n || !m)
	return MOD;
	else if((n == 1) && (m == 1))
	{
		if(!cv && (G[n-1][m-1] == '#'))
		return 1;
		else return 0;	
	}
	if(memo[n][m][cv] != -1)
	return memo[n][m][cv];
	int ans = MOD;
	if(!cv && (G[n-1][m-1] == '#'))
	{
		ans = min(ans, 1 + xd(n-1, m, cv ^ 1));
		ans = min(ans, 1 + xd(n, m-1, cv ^ 1));
	}
	else if(cv && (G[n-1][m-1] == '.'))
	{
		ans = min(ans, xd(n-1, m, cv ^ 1));
		ans = min(ans, xd(n, m-1, cv ^ 1));
	}		
	else
	{
		ans = min(ans, xd(n-1, m, cv));
		ans = min(ans, xd(n, m-1, cv));
	}
	memo[n][m][cv] = ans;
	return ans;
}

void solve(int T)
{
	memset(memo, -1, sizeof(memo));
	int h,w;
	cin>>h>>w;
	for(int i=0;i<h;i++)
	cin>>G[i];
	int fc = xd(h, w, 0);
	cout<<fc<<"\n";
	return;
}

int main(void)
{
	FLASH();
	int T;
	T = 1;

// #ifndef ONLINE_JUDGE
// 	time_t time_t1, time_t2;
// 	time_t1 = clock();
// #endif

	while(T--)
	solve(T);

// #ifndef ONLINE_JUDGE
// 	time_t2 = clock();
// 	SETF();
// 	cout<<"Time taken: "<<setprecision(7)<<(time_t2 - time_t1)/(double)CLOCKS_PER_SEC<<"\n";
// 	UNSETF();
// #endif

	return 0;
}

Measured memory_bytes: 384