#include <bits/stdc++.h>
using namespace std;
class BipartiteMatcher{
int n, m;
vector<int> l;
vector<int> r;
vector<vector<int> > graph;
vector<bool> viz;
bool pairup(int nod){
if(viz[nod] == true){
return false;
}
viz[nod] = true;
for(auto it:graph[nod]){
if(r[it] == -1){
l[nod] = it;
r[it] = nod;
return true;
}
}
for(auto it:graph[nod]){
if(pairup(r[it])){
l[nod] = it;
r[it] = nod;
return true;
}
}
return false;
}
public:
BipartiteMatcher(int n, int m) {
this->n = n;
this->m = m;
this->l = vector<int>(n, -1);
this->r = vector<int>(m, -1);
this->graph = vector<vector<int> >(n, vector<int>());
this->viz = vector<bool>(n, false);
}
void add_edge(int x, int y){
graph[x].push_back(y);
}
int solve(){
bool ok = true;
while(ok){
ok = false;
for(int i = 0;i < n;i++){
viz[i] = false;
}
for(int i = 0;i < n;i++){
if(l[i] == -1 && pairup(i)){
ok = true;
}
}
}
int cuplaj = 0;
for(int i = 0;i < n;i++){
cuplaj += (l[i] != -1);
}
return cuplaj;
}
};
int main(){
int n, m;
cin >> n >> m;
vector<string> v(n,"");
vector<vector<int> > group(n, vector<int>(m, -1));
for(int i = 0;i < n;i++){
cin >> v[i];
}
int cnt_horizontal = 0;
int cnt_vertical = 0;
for(int i = 0;i < n;i++){
for(int j = 0;j < m;j++){
if(j + 2 < m && v[i][j] == 'R' && v[i][j + 1] == 'G' && v[i][j + 2] == 'W'){
group[i][j] = cnt_horizontal;
group[i][j + 1] = cnt_horizontal;
group[i][j + 2] = cnt_horizontal;
cnt_horizontal++;
}
if(i + 2 < n && v[i][j] == 'R' && v[i + 1][j] == 'G' && v[i + 2][j] == 'W'){
cnt_vertical++;
}
}
}
BipartiteMatcher matcher(cnt_horizontal, cnt_vertical);
int last_vertical = 0;
for(int i = 0;i < n;i++){
for(int j = 0;j < m;j++){
if(i + 2 < n && v[i][j] == 'R' && v[i + 1][j] == 'G' && v[i + 2][j] == 'W'){
if(group[i][j] != -1){
matcher.add_edge(group[i][j], last_vertical);
}
if(group[i + 1][j] != -1){
matcher.add_edge(group[i + 1][j], last_vertical);
}
if(group[i + 2][j] != -1){
matcher.add_edge(group[i + 2][j], last_vertical);
}
last_vertical++;
}
}
}
printf("%d", cnt_horizontal + cnt_vertical - matcher.solve());
return 0;
}
