1 //minamoto
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<queue>
 6 #define inf 0x3f3f3f3f
 7 using namespace std;
 8 const int N=505,M=100005;
 9 int head[N],Next[M],ver[M],edge[M],cost[M],tot=1;
10 inline void add(int u,int v,int e,int c){
11     ver[++tot]=v,Next[tot]=head[u],head[u]=tot,edge[tot]=e,cost[tot]=c;
12     ver[++tot]=u,Next[tot]=head[v],head[v]=tot,edge[tot]=0,cost[tot]=-c;
13 }
14 int dis[N],vis[N],cur[N],S,T,ans;
15 queue<int> q;
16 bool spfa(){
17     memset(dis,-1,sizeof(dis));
18     memset(vis,0,sizeof(vis));
19     memcpy(cur,head,sizeof(int)*(T-S+1));
20     q.push(T),dis[T]=0,vis[T]=1;
21     while(!q.empty()){
22         int u=q.front();q.pop();vis[u]=0;
23         for(int i=head[u];i;i=Next[i])
24         if(edge[i^1]){
25             int v=ver[i],c=cost[i];
26             if(dis[v]<0||dis[v]>dis[u]-c){
27                 dis[v]=dis[u]-c;
28                 if(!vis[v]) vis[v]=1,q.push(v);
29             }
30         }
31     }
32     return ~dis[S];
33 }
34 int dfs(int u,int limit){
35     if(u==T||!limit) return limit;
36     int flow=0,f;vis[u]=1;
37     for(int i=cur[u];i;cur[u]=i=Next[i]){
38         int v=ver[i];
39         if(dis[v]==dis[u]-cost[i]&&!vis[v]&&(f=dfs(v,min(limit,edge[i])))){
40             flow+=f,limit-=f;
41             edge[i]-=f,edge[i^1]+=f;
42             ans+=f*cost[i];
43             if(!limit) break;
44         }
45     }
46     vis[u]=0;
47     return flow;
48 }
49 void zkw(){
50     while(spfa()) dfs(S,inf);
51 }
52 int id[N][N],c[N],n,m;char s[N];
53 int dx[]={0,0,-1,1},dy[]={-1,1,0,0};
54 int main(){
55     //freopen("testdata.in","r",stdin);
56     c['L']=0,c['R']=1,c['U']=2,c['D']=3;
57     scanf("%d%d",&n,&m);
58     S=0,T=n*m*2+1;
59     for(int i=1;i<=n;++i)
60     for(int j=1;j<=m;++j)
61     id[i][j]=(i-1)*m+j;
62     for(int i=1;i<=n;++i){
63         scanf("%s",s+1);
64         for(int j=1;j<=m;++j)
65         for(int k=0;k<4;++k){
66             int x=(i+dx[k]-1+n)%n+1,y=(j+dy[k]-1+m)%m+1;
67             (k==c[s[j]])?add(id[i][j],id[x][y]+n*m,1,0):add(id[i][j],id[x][y]+n*m,1,1);
68         }
69     }
70     for(int i=1;i<=n*m;++i)
71     add(S,i,1,0),add(i+n*m,T,1,0);
72     zkw();
73     printf("%d\n",ans);
74     return 0;
75 }