$RT$

#include<bits/stdc++.h>
#define int long long
using namespace std;
inline int read(){
	char ch=getchar();int s=0,f=1;
	while((ch<'0'||ch>'9')&&ch!='-') ch=getchar();
	if(ch=='-') ch=getchar(),f=-1;
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return f*s;
}
int n,m,a[100010],dp[1001][101][101];
signed main(){
	n=read();m=read();
	for(int i=1;i<=n;i++)
		for(int j=1;j<=m;j++){
			char x;
			cin>>x;
			x=(x=='P'?0:1);
			a[i]+=pow(2,m-j)*x;
		}
	for(int i=0;i<(1<<m);i++)
		if((i&(i<<1))==0&&(i&(i>>1))==0&&(i&(i<<2))==0&&(i&(i>>2))==0&&(i&a[1])==0)
			dp[1][i][0]+=__builtin_popcount(i);
	for(int i=0;i<(1<<m);i++)
		if((i&(i<<1))==0&&(i&(i>>1))==0&&(i&(i<<2))==0&&(i&(i>>2))==0&&(i&a[1])==0)
			for(int j=0;j<(1<<m);j++)
				if((j&(j<<1))==0&&(j&(j>>1))==0&&(j&(j<<2))==0&&(j&(j>>2))==0&&(j&a[2])==0&&(i&j)==0)
					dp[2][i][j]+=__builtin_popcount(i)+__builtin_popcount(j);
	for(int i=3;i<=n;i++)
		for(int j=0;j<(1<<m);j++){
			if((j&(j<<1))!=0||(j&(j>>1))!=0||(j&(j<<2))!=0||(j&(j>>2))!=0||(j&a[i])!=0)
				continue;
			for(int k=0;k<(1<<m);k++){
				if((k&(k<<1))!=0||(k&(k>>1))!=0||(k&(k<<2))!=0||(k&(k>>2))!=0||(k&a[i])!=0)
					continue;
				for(int l=0;l<(1<<m);l++){
					if((k&j)!=0||(k&l)!=0||(j&l)!=0)
						continue;
					dp[i][j][k]=max(dp[i][j][k],dp[i-1][k][l]+__builtin_popcount(j));
				}
			}
		}
	int ans=0;
	for(int i=0;i<(1<<m);i++)
		for(int j=0;j<(1<<m);j++)
			ans=max(ans,dp[n][i][j]);	
	cout<<ans;
	return 0;
}