// #pragma optimize ("g",on)
// #pragma GCC optimize ("inline")
// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC optimize ("03")
#include <bits/stdc++.h>
#define pb push_back
#define SS ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
// #define int long long
#define all(v) v.begin(),v.end()
using namespace std;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 3077, inf = 1e9, mod = 998244353;
vector<int> g[N][N];
pair<int, int> was[N][N];
int used[N][N], timer;
bool dfs(int x, int y){
if(used[x][y] == timer) return false;
used[x][y] = timer;
for(int t : g[x][y]){
if(t == 1){
bool ch = 0;
for(int i = y; i <= y + 2; i++){
if(was[x][i].first > 0 && !dfs(was[x][i].first, was[x][i].second)){
ch = 1;
break;
}
}
if(!ch){
for(int i = y; i <= y + 2; i++){
was[x][i] = {x, y};
}
return true;
}
}
if(t == 2){
bool ch = 0;
for(int i = x; i <= x + 2; i++){
if(was[i][y].first > 0 && !dfs(was[i][y].first, was[i][y].second)){
ch = 1;
break;
}
}
if(!ch){
for(int i = x; i <= x + 2; i++){
was[i][y] = {x, y};
}
return true;
}
}
}
return false;
}
void solve(){
int n, m;
cin >> n >> m;
int a[n + 1][m + 1];
char s[n + 1][m + 1];
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
char c;
cin >> c;
s[i][j] = c;
if(c == 'R') a[i][j] = 0;
if(c == 'G') a[i][j] = 1;
if(c == 'W') a[i][j] = 2;
}
}
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
if(j + 2 <= m && a[i][j] == 0 && a[i][j + 1] == 1 && a[i][j + 2] == 2){
g[i][j].push_back(1);
}
if(i + 2 <= n && a[i][j] == 0 && a[i + 1][j] == 1 && a[i + 2][j] == 2){
g[i][j].push_back(2);
}
}
}
int ans = 0, mx = 0;
// cout << g[1][1].size();
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
if(a[i][j] != 0 || was[i][j].first > 0) continue;
timer++;
if(dfs(i, j)) ans++;
}
}
mx = ans;
ans = 0;
timer = 0;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
was[i][j] = {0, 0};
used[i][j] = 0;
}
}
for(int i = n; i >= 1; i--){
for(int j = m; j >= 1; j--){
if(a[i][j] != 0 || was[i][j].first > 0) continue;
timer++;
if(dfs(i, j)) ans++;
}
}
mx = max(mx, ans);
cout << mx;
}
signed main(){
SS
// freopen("trains.in", "r", stdin);
// freopen("trains.out", "w", stdout);
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
