#include <bits/stdc++.h>
using namespace std;
#define sh short
#define ll long long
#define pll pair<ll,ll>
#define fs first
#define sc second
#define _all(a) a.begin(),a.end()
#define pii pair<short,short>
const int mxn = 3030;
struct Edge{
int to;
short cap;
Edge(){}
Edge(int tt,short cc){
to = tt,cap = cc;
}
};
vector<Edge> edges;
vector<vector<int>> paths;
vector<int> level;
string s[mxn];
int st,ed;
void addedge(int a,int b){
paths[a].push_back(edges.size());
edges.push_back(Edge(b,1));
paths[b].push_back(edges.size());
edges.push_back(Edge(a,0));
}
bool bfs(){
queue<int> q;
fill(level.begin(),level.end(),-1);
level[0] = 0;
q.push(0);
while(!q.empty()){
auto now = q.front();
q.pop();
for(auto &id:paths[now]){
if(!edges[id].cap)continue;
auto nxt = edges[id].to;
if(level[nxt] == -1){
level[nxt] = level[now]+1;
q.push(nxt);
}
}
}
return level[ed] != -1;
}
int dfs(int now,int lim){
if(now == ed)return lim;
int ans = 0;
for(auto &id:paths[now]){
if(!edges[id].cap)continue;
if(!lim)break;
auto nxt = edges[id].to;
if(level[nxt] != level[now]+1)continue;
auto re = dfs(nxt,min(edges[id].cap,(sh)lim));
if(re == 0)continue;
edges[id].cap -= re;
edges[id^1].cap += re;
ans += re;
lim -= re;
}
return ans;
}
void solve(){
int n,m;
cin>>n>>m;
for(int i =0 ;i<n;i++)cin>>s[i];
vector<pii> right,down;
for(int i = 0;i<n-2;i++){
for(int j = 0;j<m;j++){
if(s[i][j] == 'R'&&s[i+1][j] == 'G'&&s[i+2][j] == 'W')down.push_back({i,j});
}
}
for(int i = 0;i<n;i++){
for(int j = 0;j<m-2;j++){
if(s[i].substr(j,3)=="RGW")right.push_back({i,j});
}
}
sort(right.begin(),right.end());
sort(down.begin(),down.end());
paths = vector<vector<int>>(right.size()+down.size()+2);
for(int i = 0;i<right.size();i++){
pii tar = make_pair(right[i].fs-1,right[i].sc+1);
auto p1 = lower_bound(_all(down),tar)-down.begin();
if(p1 != down.size()&&down[p1].fs == right[i].fs-1&&down[p1].sc == right[i].sc+1)
addedge(i+1,p1+right.size()+1);
tar = make_pair(right[i].fs-2,right[i].sc+2);
p1 = lower_bound(_all(down),tar)-down.begin();
p1 = lower_bound(_all(down),tar)-down.begin();
if(p1 != down.size()&&down[p1].fs == right[i].fs-2&&down[p1].sc == right[i].sc+2)
addedge(i+1,p1+right.size()+1);
p1 = lower_bound(_all(down),right[i])-down.begin();
if(p1 != down.size()&&down[p1].fs == right[i].fs&&down[p1].sc == right[i].sc)
addedge(i+1,p1+right.size()+1);
}
for(int i = 1;i<=right.size();i++)addedge(0,i);
for(int i = right.size()+1;i<paths.size();i++)addedge(i,paths.size()-1);
/*
for(auto &i:down)cout<<i.fs<<' '<<i.sc<<',';cout<<endl;
for(auto &i:right)cout<<i.fs<<' '<<i.sc<<',';cout<<endl;
for(int i = 1;i<=right.size();i++){
for(auto &id:paths[i]){
if(edges[id].to == 0)continue;
cout<<i<<','<<edges[id].to<<endl;
}
}
*/
level = vector<int>(paths.size());
int ans = 0;
st = 0,ed = paths.size()-1;
while(bfs()){
int re;
while(re = dfs(0,mxn*mxn))ans+= re;
}
cout<<right.size()+down.size()-ans;
return;
}
int main(){
ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
solve();
}
