#define here cerr<<"===========================================\n"
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#define ld double
#define ll int
#define llinf 100000000000000000LL // 10^17
#define pb push_back
#define popb pop_back
#define fi first
#define sc second
#define endl '\n'
#define pll pair<ll,ll>
#define pld pair<ld,ld>
#define sz(a) (ll)(a.size())
#define all(a) a.begin(),a.end()
#define ceri(a,l,r) {for(ll i_ = l;i_<=r;i_++) cerr<<a[i_]<< " ";cerr<<endl;}
#define daj_mi_malo_vremena ios_base::sync_with_stdio(false);cerr.tie(0);cout.tie(0);cin.tie(0);
using namespace std;
using namespace __gnu_pbds;
/*
ll add(ll x,ll y){
x+=y;
if(x<0){
x%=mod;
x+=mod;
}else{
if(x>=mod) x%=mod;
}
return x;
}
ll mul(ll a,ll b){
ll ans = (a*b)%mod;
if(ans<0) ans+=mod;
return ans;
}
*/
typedef tree<int,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
typedef tree<int,null_type,less_equal<ll>,rb_tree_tag,tree_order_statistics_node_update> ordered_multiset;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll rnd(ll l,ll r){
return uniform_int_distribution<ll>(l,r)(rng);
}
#define maxn 3005
#define maxx 10000005
ll n,m;
bool vis[maxx];
ll a[maxn][maxn];
ll id[maxn][maxn][2];
ll col[maxx];
ll it = 1;
bool okright(ll i,ll j){
if(j+2>m) return 0;
return (a[i][j]==1)&&(a[i][j+1]==2)&&(a[i][j+2]==3);
}
bool okdown(ll i,ll j){
if(i+2>n) return 0;
return (a[i][j]==1)&&(a[i+1][j]==2)&&(a[i+2][j]==3);
}
bool valid(ll i,ll j){
return i>=1&&i<=n&&j>=1&&j<=m;
}
vector<ll> g[maxx];
pll dfs(ll u,ll par){
//cerr<<u<<endl;
vis[u] = 1;
col[u] = col[par]^1;
pll p = {0,(col[u]==1)};
for(ll s : g[u]){
if(s==par) continue;
pll q = dfs(s,u);
p.fi+=q.fi;
p.sc+=q.sc;
}
return p;
}
ll ans = 0;
int main(){
daj_mi_malo_vremena
cin >> n >> m;
for(ll i = 1;i<=n;i++){
string s; cin >> s;
for(ll j = 1;j<=m;j++){
if(s[j-1]=='R') a[i][j] = 1;
if(s[j-1]=='G') a[i][j] = 2;
if(s[j-1]=='W') a[i][j] = 3;
}
}
for(ll i = 1;i<=n;i++){
for(ll j = 1;j<=m;j++){
if(a[i][j]!=1) continue;
if(okright(i,j)) id[i][j][1] = it++;
if(okdown(i,j)) id[i][j][0] = it++;
if(id[i][j][1]&&id[i][j][0]){g[id[i][j][1]].pb(id[i][j][0]); g[id[i][j][0]].pb(id[i][j][1]);}
}
}
for(ll i = 1;i<=n;i++){
for(ll j = 1;j<=m;j++){
if(a[i][j]!=1) continue;
for(ll e = 1;e<=2;e++){
for(ll k = 0;k<=0;k++){
if(valid(i-e,j+e)&&id[i-e][j+e][k]&&id[i][j][k^1]) g[id[i][j][k^1]].pb(id[i-e][j+e][k]);
}
}
for(ll e = -2;e<=-1;e++){
for(ll k = 1;k<=1;k++){
if(valid(i-e,j+e)&&id[i-e][j+e][k]&&id[i][j][k^1]) g[id[i][j][k^1]].pb(id[i-e][j+e][k]);
}
}
}
}
/*
here;
for(ll i = 1;i<=n;i++){
for(ll j = 1;j<=m;j++) cerr<<id[i][j][0]<< " ";
cerr<<endl;
}
here;
for(ll i = 1;i<=n;i++){
for(ll j = 1;j<=m;j++) cerr<<id[i][j][1]<< " ";
cerr<<endl;
}
here;
*/
for(ll i = 1;i<=it-1;i++){
if(vis[i]) continue;
//cerr<<"i: "<<i<<endl;
pll p = dfs(i,i);
ans+=max(p.fi-p.sc,p.sc);
}
cout<<ans<<endl;
return 0;
}
/*
5 5
RGRGW
GRRGW
WGGWR
RWRGW
RGWGW
4 4
RGWR
GRRG
WGGW
WWWR
3 4
RGWR
GRGG
RGWW
*/
