#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using ordered_set = tree<T,null_type,less_equal<T>,rb_tree_tag,
tree_order_statistics_node_update>;
#define ll long long
#define pi pair<int,int>
#define vi vector<int>
#define pb push_back
#define all(a) a.begin(),a.end()
void solve(){
int n,m; cin >> n >> m;
int cnt = 0;
vector<char> last(m,'B'), now(m);
int ans = 0;
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++) cin >> now[j];
for(int j = 0; j < m-2; j++){
if(now[j]=='R' && now[j+1]=='G' && now[j+2]=='W'){
ans++; now[j] = now[j+1] = now[j+2] = 'B';
}
}
for(int j = 0; j < m; j++){
if(now[j]=='W' && last[j]=='G')
last[j] = 'B', ans++;
else if(now[j]=='G' && last[j]=='R')
last[j] = 'G';
else if(now[j]=='R') last[j] = 'R';
else last[j] = 'B';
}
}
cout << ans << '\n';
}
signed main(){
cin.tie(0)->sync_with_stdio(0);
int t = 1;
while(t--) solve();
}
