#include<bits/stdc++.h>

#define debug(x) cerr << #x << ": " << x << '\n'
#define debugArray(x,n) for(long long hoge = 0; (hoge) < (n); ++ (hoge)) cerr << #x << "[" << hoge << "]: " << x[hoge] << '\n'
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<ll> vll;
const ll INF = LLONG_MAX/2;
const ll MOD = 1e9+7;

struct bipartiteGraph{
  int L, R;
  vector<vector<int>> adj;
  vector<int> mate;
  bipartiteGraph(int L, int R) : L(L), R(R), adj(L+R),mate(L+R, -1) { }
  void add_edge(int u, int v) {
    adj[u].push_back(v+L);
    adj[v+L].push_back(u);
  }
  int maximum_matching() {
    vector<int> level(L);

    function<bool(void)> levelize = [&]() { // BFS
      queue<int> Q;
      for (int u = 0; u < L; ++u) {
        level[u] = -1;
        if (mate[u] < 0) {
          level[u] = 0;
          Q.push(u);
        }
      }
      while (!Q.empty()) {
        int u = Q.front(); Q.pop();
        for (int w: adj[u]) {
          int v = mate[w];
          if (v < 0) return true;
          if (level[v] < 0) {
            level[v] = level[u] + 1;
            Q.push(v);
          }
        }
      }
      return false;
    };
    function<bool(int)> augment = [&](int u) { // DFS
      for (int w: adj[u]) {
        int v = mate[w];
        if (v < 0 || (level[v] > level[u] && augment(v))) {
          mate[u] = w;
          mate[w] = u;
          return true;
        }
      }
      return false;
    };
    int match = 0;
    while (levelize())
      for (int u = 0; u < L; ++u)
        if (mate[u] < 0 && augment(u))
          ++match;
    return match;
  }
  int lPartner(int l){
    return mate[l]-L;
  }
  int rPartner(int r){
    return mate[r+L];
  }
};

signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll N,M;cin>>N>>M;
  vector<string> S(N);
  ll bsize=0,wsize=0;
  for(ll i=0;i<N;i++){
    cin>>S[i];
    for(ll j=0;j<M;j++){
      bsize += S[i][j]=='b';
      wsize += S[i][j]=='w';
    }
  }
  bipartiteGraph g(N*M,N*M);
  for(ll i=0;i<N;i++){
    for(ll j=0;j<M;j++)if((i+j)&1&&S[i][j]=='b'){
      if(i>0&&S[i-1][j]=='w')g.add_edge(i*M+j,(i-1)*M+j);
      if(i+1<N&&S[i+1][j]=='w')g.add_edge(i*M+j,(i+1)*M+j);
      if(j>0&&S[i][j-1]=='w')g.add_edge(i*M+j,i*M+j-1);
      if(j+1<M&&S[i][j+1]=='w')g.add_edge(i*M+j,i*M+j+1);
    }
  }
  ll x=g.maximum_matching();
  if(bsize>wsize)swap(bsize,wsize);
  ll ans = 100*x+10*(bsize-x)+wsize-bsize;
  cout<<ans<<endl;
  return 0;
}