#include <bits/stdc++.h>
using namespace std;
#define lef(x) (x<<1)
#define rig(x) (lef(x)|1)
typedef long long int ll;
typedef unsigned long long int ull;
typedef long double ld;
const int MAX = 4e3+10;
const ll mod = 998244353;
const int inf = 1e9;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
struct info{
int x,y;
char c;
info(int x,int y, char c) : x(x), y(y), c(c){}
};
char a[MAX][MAX];
vector<pair<int,int>> movs = {{1,0},{-1,0},{0,1},{0,-1}};
int solve(int n,int m){
int ans = 1;
deque<info> q;
char at = a[n-1][m-1];
a[n-1][m-1] = '.';
q.push_front(info(n-1,m-1,at));
while(!q.empty()){
auto [x,y,c] = q.front();
if(at != c) {
ans++;
at = c;
}
q.pop_front();
for(auto v : movs){
int x2,y2;
x2 = x + v.first;
y2 = y + v.second;
if(x2 < 0 || x2 >= n || y2 < 0 || y2 >= m || a[x2][y2] == '.') continue;
if(a[x2][y2] == at) q.push_front(info(x2,y2,a[x2][y2]));
else q.push_back(info(x2,y2,a[x2][y2]));
a[x2][y2] = '.';
}
}
return ans;
}
void test() {
int n,m;
cin >> n >> m;
for(int i=0; i<n; i++) for(int j=0; j<m; j++) cin >> a[i][j];
cout << solve(n,m) << '\n';
}
int32_t main() {
ios::sync_with_stdio(false), cin.tie(nullptr);
int t=1;
// cin >> t;
while(t--) test();
return 0;
}
