#include <bits/stdc++.h>

using namespace std;

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int n,m,val;
	int sumCM[1001][1001];
	cin>>m>>n;
	char aux;
	for(int i = 0; i < m; i++){
		for(int j = 0; j < n; j++){
			cin>>aux;
			if(aux == 'M'){
				sumCM[i][j] = 0;
			}else if(aux == 'C'){
				sumCM[i][j] = 1;
			}
		}
	}
	cin>>val;
	int maxi = -1;
	    int SOMA[1001][1001];
	    for (int i = 0; i <= n; i++)
		SOMA[0][i] = 0;
	    for (int i = 0; i <= m; i++)
		SOMA[i][0] = 0;

	    for (int i = 1; i <= n; i++){
		SOMA[1][i] = SOMA[1][i-1] + sumCM[0][i-1];
	    }

	    for (int i = 1; i <= m; i++){
		SOMA[i][1] = SOMA[i-1][1] + sumCM[i-1][0];
	    }

	    for(int i = 1; i <= m; i++){
		for(int j = 1; j <= n; j++){
			SOMA[i][j] = SOMA[i-1][j] + SOMA[i][j-1]-SOMA[i-1][j-1]+sumCM[i-1][j-1];
		}
	    }

 	    for(int i = val; i <= m ; i++){
		for(int j = val; j <= n; j++){
			int soma = SOMA[i][j] - (SOMA[i-val][j]+SOMA[i][j-val])+SOMA[i-val][j-val];
			if(soma != 0 && soma != val*val)maxi = max(maxi,soma);
		}
	    }
		if(maxi == -1)cout<<-1<<endl;
		else cout<<maxi*25+((val*val)-maxi)*12<<endl;

	return 0;
}