#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
#define ll long long
// #define int long long
#define pb push_back
#define fi first
#define se second
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
#define ld long double
using namespace std;
typedef pair<int,int> pii;
typedef pair<int, pii> ipii;
const int MAXN = 3010;
const int MAXA = 9e6+10;
const int INF = 1e9+10;
const int LOG = 19;
const int MOD = 1e9+7;
const int SQRT = 450;
const vector<int> NOL = {};
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const vector<int> dx = {1, -1, 0, 0};
const vector<int> dy = {0, 0, 1, -1};
int n, m;
char a[MAXN][MAXN];
int b[MAXN][MAXN], cnt;
vector <int> adj[MAXA];
void add(int x, int y){ adj[x].pb(y); adj[y].pb(x); }
int day, mat[MAXA], vis[MAXA];
bool done[MAXA];
bool dfs(int nw){
if(vis[nw] == day) return 0;
vis[nw] = day;
for(auto nx : adj[nw]){
if(mat[nx]==0 || dfs(mat[nx])){
mat[nx] = nw; return 1;
}
}
return 0;
}
signed main(){
// ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> n >> m;
for(int i=1; i<=n; i++)
for(int j=1; j<=m; j++) cin >> a[i][j];
for(int i=1; i<=n; i++){
for(int j=1; j<=m-2; j++){
if(a[i][j]=='R' && a[i][j+1]=='G' && a[i][j+2]=='W'){
b[i][j] = ++cnt;
b[i][j+1] = cnt;
b[i][j+2] = cnt;
}
}
}
int num = cnt;
for(int i=1; i<=n-2; i++){
for(int j=1; j<=m; j++){
if(a[i][j]=='R' && a[i+1][j]=='G' && a[i+2][j]=='W'){
++cnt;
add(cnt, b[i][j]);
add(cnt, b[i+1][j]);
add(cnt, b[i+2][j]);
}
}
}
int ANS = 0;
for(int i=1; i<=num; i++){
for(auto nx : adj[i]){
if(mat[nx] == 0){
mat[nx] = i;
done[i] = 1;
ANS++;
break;
}
}
}
for(int i=1; i<=num; i++){
if(done[i]) continue;
day++;
ANS += dfs(i);
}
cout << cnt-ANS << '\n';
}
