#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <queue>
using namespace std;
typedef pair<int,int> ii;
int r,c;
char arr[4005][4005];
bool pushed[4005][4005];
queue<ii> q;
int dx[]={1,-1,0,0},dy[]={0,0,1,-1};
void print(){
for (int x=1;x<=r;x++){
for (int y=1;y<=c;y++){
printf("%c",arr[x][y]);
}
printf("\n");
}
printf("\n");
}
void dfs(int i,int j,char a){
for (int x=0;x<4;x++){
if (i+dx[x]<1 || i+dx[x]>r || j+dy[x]<1 || j+dy[x]>c) continue;
if (arr[i+dx[x]][j+dy[x]]==a){
arr[i+dx[x]][j+dy[x]]='.';
dfs(i+dx[x],j+dy[x],a);
}
else if (arr[i+dx[x]][j+dy[x]]!='.'){
if (!pushed[i+dx[x]][j+dy[x]])q.push(ii(i+dx[x],j+dy[x])),pushed[i+dx[x]][j+dy[x]]=true;
}
}
}
int main(){
char curr_animal='?';
int ans=0;
//freopen("input.txt","r",stdin);
scanf("%d%d",&r,&c);
for (int x=1;x<=r;x++){
getchar();
for (int y=1;y<=c;y++){
arr[x][y]=getchar();
}
}
q.push(ii(1,1));
q.push(ii(r,c));
int a,b;
while (!q.empty()){
a=q.front().first,b=q.front().second,q.pop();
//printf("%d %d\n",a,b);
if (arr[a][b]=='.') continue;
if (curr_animal!=arr[a][b]) curr_animal=arr[a][b],ans++;
arr[a][b]='.';
dfs(a,b,curr_animal);
}
printf("%d\n",ans);
}
