RT

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

int n, m, cnt = 0;
int ss[105], ok[62], numk[62];
int f[105][66][66];

void ycl() {
	for(int s = 0; s <= (1 << m) - 1; s++) {
		if((((s << 1) | (s << 2) | (s >> 1) | (s >> 2)) & s) == 0) {
			ok[++cnt] = s;
			int s1 = s, k = 0;
			while(s1) {
				if(s1 & 1) k++;
				s1 >>= 1; 
			}
			numk[cnt] = k;
		}
	}
	return;
}

int main() {
	scanf("%d%d", &n, &m);
	ycl();
	for(int i = 1; i <= n; i++) {
		for(int j = 1; j <= m; j++) {
			char ch = getchar();
			if(ch == 'P') ss[i] = ss[i] << 1 | 1;
			if(ch == 'H') ss[i] = ss[i] << 1;
		}
		char ch = getchar();
	}
	
	for(int i = 1; i <= cnt; i++) if(ok[i] & ss[1] == 0) f[1][0][i] = numk[i]; 
	// ycl第一行 
	if(n >= 2) {
		for(int i = 1; i <= cnt; i++) {
			for(int j = 1; j <= cnt; j++) {
				if(!(ok[i] & ok[j]) && !(ok[j] & ss[2]) && !(ok[i] & ss[2])) f[2][i][j] = max(f[2][i][j], f[1][0][i] + numk[j]);
			}
		} 
	}											
	// ycl第二行 
	for(int i = 3; i <= n; i++) {
		for(int now = 1; now <= cnt; now++) {
			for(int lst1 = 1; lst1 <= cnt; lst1++) {
				for(int lst2 = 1; lst2 <= cnt; lst2++) {
					if(!(ok[lst2] & ok[lst1]) && !(ok[lst1] & ok[now]) && !(ok[lst2] & ok[now]) && !(ok[lst2] & ss[i]) && !(ok[lst1] & ss[i]) && !(ok[now] & ss[i])) f[i][lst1][now] = max(f[i][lst1][now], f[i - 1][lst2][lst1] + numk[now]);
				}
			}
		}
	}
	//dp
	int mx = -1;
	for(int lst1 = 1; lst1 <= cnt; lst1++) {
		for(int lst2 = 1; lst2 <= cnt; lst2++) {
			mx = max(mx, f[n][lst2][lst1]);
		}
	}
	printf("%d", mx);
}