#include<bits/stdc++.h>using namespace std;

int n,m,state[1<<10],tot=0;

int dp[110][66][66],sum[1<<10],mp[110];

int getsum(int x){    int cnt=0;    while(x){        if(x&1) cnt++;        x>>=1;    }    return cnt;}

bool check(int x){    if(x&(x>>1)) return 0;    if(x&(x>>2)) return 0;    return 1;}

int main(){    memset(dp,0,sizeof(dp));    scanf("%d%d",&n,&m);    for(int i=0;i<(1<<m);i++){        if(check(i))         {            state[++tot]=i;            sum[tot]=getsum(i);        }    }    for(int i=1;i<=n;i++) for(int j=0;j<m;j++)    {        char ch=getchar();        while(ch!='P' && ch!='H') ch=getchar();        if(ch=='H') mp[i]+=(1<<(m-1-j));    }    //处理第一行     for(int i=1;i<=tot;i++){        if(state[i]&mp[1]) continue;        dp[1][i][0]=sum[i];    }    //处理第二行    for(int i=1;i<=tot;i++){        if(mp[2]&state[i]) continue;        for(int j=1;j<=tot;j++){            if(mp[1]&state[j]) continue;            if(state[i]&state[j]) continue;            dp[2][i][j]=max(dp[2][i][j],dp[1][j][0]+sum[i]);        }    }

    for(int i=3;i<=n;i++){        for(int k1=1;k1<=tot;k1++){            if(state[k1]&mp[i]) continue;            for(int k2=1;k2<=tot;k2++){                if(state[k2]&mp[i-1]) continue;                if(state[k2]&state[k1]) continue;                for(int k3=1;k3<=tot;k3++){                    if(state[k3]&mp[i-2]) continue;                    if(state[k3]&state[k2]) continue;                    if(state[k3]&state[k1]) continue;                    dp[i][k1][k2]=max(dp[i][k1][k2],dp[i-1][k2][k3]+sum[k1]);                }            }        }    }    int ans=0;    for(int i=1;i<=tot;i++){        for(int j=1;j<=tot;j++){            ans=max(ans,dp[n][i][j]);        }    }    printf("%d",ans);    return 0;}