#include <stdio.h>
#include <stdlib.h>

int main()
{
	int i, N, M;
	char **S;
	scanf("%d %d", &N, &M);
	S = (char**)malloc(sizeof(char*) * (N + 1));
	for (i = 0; i < N; i++) {
		S[i] = (char*)malloc(sizeof(char) * (M + 1));
		scanf("%s", S[i]);
	}
	
	int j;
	char T[2][1000003];
	for (j = 0; j < M; j++) {
		if (S[0][j] == S[1][j]) {
			T[0][j] = S[0][j];
			T[1][j] = S[1][j];
		} else break;
	}
	T[0][j] = S[0][j];
	T[1][j] = S[1][j];
	for (; j < M; j++) {
		T[0][j+1] = S[1][j];
		T[1][j+1] = S[0][j];
	}
	T[0][j+1] = 0;
	T[1][j+1] = 0;
	
	int ans[2] = {1, 1};
	for (i = 0; i < N; i++) {
		for (j = 0; j < M; j++) if (T[0][j] != S[i][j]) break;
		for (; j < M; j++) if (T[0][j+1] != S[i][j]) break;
		if (j < M) ans[0] = 0;
		for (j = 0; j < M; j++) if (T[1][j] != S[i][j]) break;
		for (; j < M; j++) if (T[1][j+1] != S[i][j]) break;
		if (j < M) ans[1] = 0;
	}
	printf("%d\n", ans[0] + ans[1]);
	fflush(stdout);
	return 0;
}