#include <bits/stdc++.h>
using namespace std;
struct HopcroftKarp {
int n, m;
vector<vector<int>> adj;
vector<int> dist, pairU, pairV;
const int INF = 1e9;
HopcroftKarp(int n, int m): n(n), m(m) {
adj.assign(n, {});
pairU.assign(n, -1);
pairV.assign(m, -1);
dist.assign(n, 0);
}
void addEdge(int u, int v) {
adj[u].push_back(v);
}
bool bfs() {
queue<int> Q;
for(int i = 0; i < n; i++) {
if(pairU[i] == -1) {
dist[i] = 0;
Q.push(i);
} else {
dist[i] = INF;
}
}
bool found = false;
while(!Q.empty()) {
int u = Q.front();
Q.pop();
if(dist[u] < INF) {
for(int v : adj[u]) {
if(pairV[v] == -1) {
found = true;
} else if(dist[pairV[v]] == INF) {
dist[pairV[v]] = dist[u] + 1;
Q.push(pairV[v]);
}
}
}
}
return found;
}
bool dfs(int u) {
for(int v : adj[u]) {
if(pairV[v] == -1 || (dist[pairV[v]] == dist[u] + 1 && dfs(pairV[v]))) {
pairU[u] = v;
pairV[v] = u;
return true;
}
}
dist[u] = INF;
return false;
}
int maximumMatching() {
int result = 0;
while(bfs()) {
for(int i = 0; i < n; i++) {
if(pairU[i] == -1 && dfs(i)) {
result++;
}
}
}
return result;
}
};
int main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
int n, m;
if(!(cin >> n >> m)) return 0;
vector<string> grid(n);
for(int i = 0; i < n; i++){
cin >> grid[i];
}
vector<vector<int>> vert_index(n, vector<int>(m, -1));
vector<vector<int>> horz_index(n, vector<int>(m, -1));
int Vcount = 0, Hcount = 0;
// Tìm các đoạn dọc R-G-W
for(int i = 0; i+2 < n; i++){
for(int j = 0; j < m; j++){
if(grid[i][j]=='R' && grid[i+1][j]=='G' && grid[i+2][j]=='W'){
vert_index[i][j] = Vcount;
vert_index[i+1][j] = Vcount;
vert_index[i+2][j] = Vcount;
Vcount++;
}
}
}
// Tìm các đoạn ngang R-G-W
for(int i = 0; i < n; i++){
for(int j = 0; j+2 < m; j++){
if(grid[i][j]=='R' && grid[i][j+1]=='G' && grid[i][j+2]=='W'){
horz_index[i][j] = Hcount;
horz_index[i][j+1] = Hcount;
horz_index[i][j+2] = Hcount;
Hcount++;
}
}
}
// Xây dựng đồ thị: nối đỉnh dọc i với ngang j nếu chúng chia sẻ ô
HopcroftKarp hk(Vcount, Hcount);
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
int v = vert_index[i][j];
int h = horz_index[i][j];
if(v != -1 && h != -1){
hk.addEdge(v, h);
}
}
}
int match = hk.maximumMatching();
int total = Vcount + Hcount;
int answer = total - match;
cout << answer;
return 0;
}
