#include<bits/stdc++.h>
using namespace std;
const int N = 3001;
int n, m, nr;
int matched[N * N], vis[N * N], rep[N][N];
int iter;
bool horiz[N][N], vert[N][N];
string tab[N];
vector<int> g[N * N];
bool match(int x) {
vis[x] = iter;
for(int i: g[x]) {
if(matched[i] == -1) {
matched[i] = x;
return true;
}
}
for(int i: g[x]) {
if(vis[matched[i]] != iter && match(matched[i])) {
matched[i] = x;
return true;
}
}
return false;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin>>n>>m;
for(int i=n-1; i>=0; --i) {
cin>>tab[i];
}
for(int i=0; i<n; ++i) { // left - right
for(int j=0; j+2<m; ++j) {
if(tab[i][j] == 'R' && tab[i][j+1] == 'G' && tab[i][j+2] == 'W') {
vert[i][j] = 1;
}
}
}
for(int i=2; i<n; ++i) { // top - bottom
for(int j=0; j<m; ++j) {
if(tab[i][j] == 'R' && tab[i-1][j] == 'G' && tab[i-2][j] == 'W') {
horiz[i][j] = 1;
rep[i][j] = nr;
nr++;
}
}
}
int sz = 0;
for(int i=0; i<n; ++i) {
for(int j=0; j<m; ++j) {
if(vert[i][j]) {
if(horiz[i][j]) {
g[sz].push_back(rep[i][j]);
}
if(i+1<n && j+1<m && horiz[i+1][j+1]) {
g[sz].push_back(rep[i+1][j+1]);
}
if(i+2<n && j+2<m && horiz[i+2][j+2]) {
g[sz].push_back(rep[i+2][j+2]);
}
sz++;
}
}
}
for(int i=0; i<nr; ++i) {
matched[i] = -1;
}
int ans = 0;
for(int i=0; i<sz; ++i) {
iter++;
match(i);
}
for(int i=0; i<nr; ++i) {
if(matched[i] != -1) {
ans++;
}
}
cout<<nr + sz - ans;
}
