#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define ins insert
#define all(x) x.begin(), x.end()
#define F first
#define S second
const int N = 10001000;
char a[3001][3001];
vector<int>g[N];
int used[N], mt[N], timer, n, m;
bool dfs(int v){
if(used[v] == timer) return false;
used[v] = timer;
for(auto to : g[v]){
if(!mt[to]){
mt[to] = v;
mt[v] = to;
return true;
}
}
for(auto to : g[v]){
if(dfs(mt[to])){
mt[to] = v;
mt[v] = to;
return true;
}
}
return false;
}
int func(int i, int j){
return (i - 1) * m + j;
}
void solve(){
cin>>n>>m;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
cin>>a[i][j];
}
}
int cnt = n * m;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
cnt++;
if(i + 2 <= n){
if(a[i][j] == 'R'&& a[i + 1][j] == 'G' && a[i + 2][j] == 'W'){
g[cnt].pb(func(i + 2, j));
}
}
if(j + 2 <= m){
if(a[i][j] == 'R'&& a[i][j + 1] == 'G'&& a[i][j + 2] == 'W'){
g[cnt].pb(func(i, j + 2));
}
}
if(i - 2 >= 1){
if(a[i][j] == 'R' && a[i - 1][j] == 'G' && a[i - 2][j] == 'W'){
g[cnt].pb(func(i - 2, j));
}
}
if(j - 2 >= 1){
if(a[i][j] == 'R' && a[i][j - 1] == 'G' && a[i][j - 2] == 'W'){
g[cnt].pb(func(i, j - 2));
}
}
}
}
int ans = 0;
for(int i = n * m + 1; i <= cnt; i++){
timer++;
if(dfs(i)){
ans++;
}
}
cout<<ans;
}
signed main(){
ios_base :: sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int t = 1;
//cin>>t;
while(t--){
solve();
}
}
