#include<cstdio>

 #include<algorithm>

 #include<cmath>

 #include<iostream>

 #include<cstring>

 #include<queue>

 using namespace std;

 const int lx[]={,,,-},ly[]={,,-,};

 const int INF=1e9+,NN=**+,MM=;

 int n,m,S,T;

 int cnt,head[NN],next[MM],rea[MM],val[MM],cost[MM];

 int dis[NN],flag[NN],a[NN][NN],mark[NN][NN];

 char s[];

 struct Node

 {

     int e,fa;

     void init(){e=fa=-;}

 }pre[NN];

 void add(int u,int v,int fee,int fare)

 {

     cnt++;

     next[cnt]=head[u];

     head[u]=cnt;

     rea[cnt]=v;

     val[cnt]=fee;

     cost[cnt]=fare;

 }

 void build()

 {

     int adq=n*m,nx,ny;

     for (int i=;i<=n;i++)

         for (int j=;j<=m;j++)

             for (int k=;k<;k++)

             {

                 nx=i+lx[k],ny=j+ly[k];

                 if (nx<) nx=n;

                 if (ny<) ny=m;

                 if (nx>n) nx=;

                 if (ny>m) ny=;

                 if (a[i][j]==k) add(mark[i][j],mark[nx][ny]+adq,,),add(mark[nx][ny]+adq,mark[i][j],,);

                 else add(mark[i][j],mark[nx][ny]+adq,,),add(mark[nx][ny]+adq,mark[i][j],,-);

             }

     for (int i=;i<=n;i++)

         for (int j=;j<=m;j++)

         {

             add(S,mark[i][j],,),add(mark[i][j],S,,);

             add(mark[i][j]+adq,T,,),add(T,mark[i][j]+adq,,);

         }

 }

 bool Spfa()

 {

     for (int i=;i<=T;i++)

     {

         flag[i]=;

         dis[i]=INF;

         pre[i].init();

     }

     queue<int>q;

     while (!q.empty()) q.pop();

     q.push(S);

     dis[S]=,flag[S]=;

     while (!q.empty())

     {

         int u=q.front();

         q.pop();

         for (int i=head[u];i!=-;i=next[i])

         {

             int v=rea[i],fee=cost[i];

             if (dis[u]+fee<dis[v]&&val[i]>)

             {

                 dis[v]=dis[u]+fee;

                 pre[v].e=i;

                 pre[v].fa=u;

                 if (flag[v]==)

                 {

                     flag[v]=;

                     q.push(v);

                 }

             }

         }

         flag[u]=;

     }

     if (dis[T]==INF) return ;

     else return ;

 }

 int MFMC()

 {

     int res=;

     while (Spfa())

     {

         int x=INF;

         for (int i=T;pre[i].fa!=-;i=pre[i].fa)

         {

             int e=pre[i].e;

             x=min(x,val[e]);

         }

         res+=x*dis[T];

         for (int i=T;pre[i].fa!=-;i=pre[i].fa)

         {

             int e=pre[i].e;

             val[e]-=x,val[e^]+=x;

         }

     }

     return res;

 }

 int main()

 {

     cnt=;

     memset(head,-,sizeof(head));

     scanf("%d%d",&n,&m);

     for (int i=;i<=n;i++)

     {

         scanf("%s",s);

         for (int j=;j<m;j++)

         {

             mark[i][j+]=(i-)*m+j+;

             if (s[j]=='R') a[i][j+]=;

             if (s[j]=='D') a[i][j+]=;

             if (s[j]=='L') a[i][j+]=;

             if (s[j]=='U') a[i][j+]=;

         }

     }

     S=n*m*+,T=n*m*+;

     build();

     printf("%d\n",MFMC());

 }