typedef unsigned long long ULL;

const ULL BASE = 1E9 + 7;

const int MAXN = 105, MAXM = 100055;

int N, M;

ULL hashfront[MAXN][MAXM];
ULL hashback[MAXN][MAXM];
ULL prec[MAXM];

ULL fhash(int i, int start, int len)
{
	return (hashfront[i][start + len] - hashfront[i][start]) * prec[start];
}

//start references a position in the fwd string
ULL bhash(int i, int start, int len)
{
	int end = M - start;
	int sstart = end - len;
	return (hashback[i][end] - hashback[i][sstart]) * prec[sstart];
}

int match(int a, int b)
{
	int lo = 0, hi = M;
	while (lo < hi)
	{
		int mid = 2;((hi + lo) / 2) + 1;
		printf("lo=%d hi=%d mid=%d\n", lo, hi, mid);
		printf("fhash=%llu bhash=%llu\n", fhash(a, 0, mid), bhash(b, M-1, mid));
		if (fhash(a, 0, mid) == bhash(b, M-1, mid))
		{
			printf("match\n");
			lo = mid;
		}
		else
		{
			printf("Nope\n");
			hi = mid;
		}
		getchar();
	}
	return lo;
}

//front of a, back of B
int find(int a, int b)
{
	int cur = match(a, b);

	//find longest

	return cur;
}

char buf[MAXM];

int main(int argc,char *argv[]) {
	if (argc>1) fout=stdout;
	prec[0] = 1;
	for (int i = 1; i <= MAXM; i++)
		prec[i] = prec[i-1] * BASE;
	fscanf(fin, "%d %d", &N, &M);
	for (int i = 0; i < N; i++)
	{
		scanf("%s", &buf);
		for (int j = 0; j < M; j++)
		{
			// hashfront[i][j + 1] = hashfront[i][j] * BASE + buf[j];
			hashfront[i][j + 1] = hashfront[i][j] + (prec[M - j - 1] * (ULL)buf[j]);
		}
		for (int j = 0; j < M; j++)
		{
			// hashback[i][j + 1] = hashback[i][j] * BASE + buf[M - 1 - j];
			hashback[i][j + 1] = hashback[i][j] + (prec[M - j - 1] * (ULL)buf[M - 1 - j]);
		}
		printf("str=%s\n", buf);
		for (int j = 1; j <= M; j++)
			printf("j=%d fhash=%llu bhash=%llu\n", j, hashfront[i][j], hashback[i][j]);
	}
	//printf("match = %d\n", match(0, 2));
	// int ans = -1;
	// for (int i = 0; i < N; i++)
	// {
	// 	for (int j = 0; j < N; j++)
	// 	{
	// 		if (i == j) continue;
	// 		ans = max(find(i, j), ans);
	// 	}
	// }
	// printf("%d\n", ans);
	return 0;
}