#include <bits/stdc++.h>

using namespace std;

struct Bipartite_Matching
{
  vector< vector< int > > graph;
  vector< int > match;
  vector< bool > used;

  Bipartite_Matching(int n)
  {
    graph.resize(n);
  }

  void add_edge(int u, int v)
  {
    graph[u].push_back(v);
    graph[v].push_back(u);
  }

  bool dfs(int v)
  {
    used[v] = true;
    for(int i = 0; i < graph[v].size(); i++) {
      int u = graph[v][i], w = match[u];
      if(w == -1 || (!used[w] && dfs(w))) {
        match[v] = u;
        match[u] = v;
        return (true);
      }
    }
    return (false);
  }

  int bipartite_matching()
  {
    int ret = 0;
    match.assign(graph.size(), -1);
    for(int i = 0; i < graph.size(); i++) {
      if(match[i] == -1) {
        used.assign(graph.size(), false);
        ret += dfs(i);
      }
    }
    return (ret);
  }
};


int main()
{
  int N, M;
  string S[50];
  int A = 0, B = 0;

  cin >> N >> M;
  for(int i = 0; i < N; i++) {
    cin >> S[i];
    for(int j = 0; j < M; j++) {
      A += S[i][j] == 'w';
      B += S[i][j] == 'b';
    }
  }

  Bipartite_Matching flow(N * M);
  for(int i = 0; i < N; i++) {
    for(int j = 1; j < M; j++) {
      if(S[i][j - 1] == 'w' && S[i][j] == 'b') flow.add_edge(i * M + j - 1, i * M + j);
      if(S[i][j - 1] == 'b' && S[i][j] == 'w') flow.add_edge(i * M + j - 1, i * M + j);
    }
  }
  for(int i = 1; i < N; i++) {
    for(int j = 0; j < M; j++) {
      if(S[i - 1][j] == 'w' && S[i][j] == 'b') flow.add_edge(i * M + j - M, i * M + j);
      if(S[i - 1][j] == 'b' && S[i][j] == 'w') flow.add_edge(i * M + j - M, i * M + j);
    }
  }

  int ret = flow.bipartite_matching();
  A -= ret;
  B -= ret;
  ret *= 100;
  ret += min(A, B) * 10;
  int get = min(A, B);
  A -= get;
  B -= get;
  ret += A;
  ret += B;
  cout << ret << endl;
}