#include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
#define pii pair<int,int>
const int dir[4][2]= {{0,-1}, {-1,0}, {0,1}, {1,0}};
void solve() {
int n,m; cin>>n>>m;
string str[n];
for(int i=0; i<n; i++) cin>>str[i];
int vis[n][m]; memset(vis,0,sizeof(vis));
int ans=0;
deque<pii> dq;
dq.push_back({0,0});
pii tp;
vis[0][0]=1;
int dp[n][m]; memset(dp,0,sizeof(dp));
dp[0][0]=1;
while(dq.size()) {
tp=dq.front(); dq.pop_front();
ans=dp[tp.f][tp.s];
for(int i=0; i<4; i++) {
int ni=dir[i][0]+tp.f, nj= dir[i][1]+tp.s;
if(ni >=0 && ni<n && nj>=0 && nj<m && !vis[ni][nj] && str[ni][nj]!='.') {
if(str[ni][nj]!=str[tp.f][tp.s]) dq.push_back({ni,nj}),dp[ni][nj]=ans+1;
else dq.push_front({ni,nj}),dp[ni][nj]=ans;
vis[ni][nj]=1;
}
}
}
cout<<ans<<"\n";
}
int main() {
ios_base::sync_with_stdio(false), cin.tie(NULL);
int t = 1; while (t--) solve();
return 0;
}
