#include <cmath>

#include <cstdio>

#include <cstring>

#include <iostream>

#define N 1010000

using namespace std;

int n, m, t, cnt, len, ans, mx, mn = 1e9;

int pos[N], a[N / 1000], num[N / 1000], sa[N], height[N], Rank[N], b[N], x[N], y[N], d[N][22], s[N];

inline int read()

{

	int x = 0, f = 1;

	char ch = getchar();

	for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -1;

	for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - '0';

	return x * f;

}

inline void build_sa()

{

	int i, k, p;

	for(i = 0; i < m; i++) b[i] = 0;

	for(i = 0; i < n; i++) b[x[i] = s[i]]++;

	for(i = 1; i < m; i++) b[i] += b[i - 1];

	for(i = n - 1; i >= 0; i--) sa[--b[x[i]]] = i;

	for(k = 1; k <= n; k <<= 1)

	{

		p = 0;

		for(i = n - k; i < n; i++) y[p++] = i;

		for(i = 0; i < n; i++) if(sa[i] >= k) y[p++] = sa[i] - k;

		for(i = 0; i < m; i++) b[i] = 0;

		for(i = 0; i < n; i++) b[x[y[i]]]++;

		for(i = 1; i < m; i++) b[i] += b[i - 1];

		for(i = n - 1; i >= 0; i--) sa[--b[x[y[i]]]] = y[i];

		swap(x, y);

		p = 1, x[sa[0]] = 0;

		for(i = 1; i < n; i++)

			x[sa[i]] = y[sa[i]] == y[sa[i - 1]] && y[sa[i] + k] == y[sa[i - 1] + k] ? p - 1 : p++;

		if(p >= n) break;

		m = p;

	}

}

inline void build_height()

{

	int i, j, k = 0;

	for(i = 0; i < n; i++) Rank[sa[i]] = i;

	for(i = 0; i < n; i++)

	{

		if(k) k--;

		j = sa[Rank[i] - 1];

		while(s[i + k] == s[j + k]) k++;

		height[Rank[i]] = k;

	}

}

inline void build_st()

{

	int i, j;

	for(i = 1; i < n; i++) d[i][0] = height[i];

	for(j = 1; (1 << j) < n; j++)

		for(i = 1; i + (1 << j) - 1 < n; i++)

			d[i][j] = min(d[i][j - 1], d[i + (1 << j - 1)][j - 1]);

}

inline int query(int l, int r)

{

	l++;

	if(l > r) return 0;

	int tmp = log2(r - l + 1);

	return min(d[l][tmp], d[r - (1 << tmp) + 1][tmp]);

}

inline void solve()

{

	int i, j = 0;

	for(i = 0; i < n; i++)

	{

		while(j < n && cnt < t)

		{

			if(!num[pos[sa[j]]]++ && pos[sa[j]]) cnt++;

			j++;

		}

		if(cnt == t) ans = max(ans, query(i, j - 1));

		if(!--num[pos[sa[i]]] && pos[sa[i]]) cnt--;

	}

}

int main()

{

	int i, j, k;

	t = read();

	for(i = 1; i <= t; i++)

	{

		k = read();

		for(j = 1; j <= k; j++) a[j] = read();

		for(j = 1; j < k; j++)

		{

			pos[n] = i;

			s[n++] = a[j + 1] - a[j];

			mn = min(mn, s[n - 1]);

		}

		s[n++] = mx++;

	}

	for(i = 0; i < n; i++)

		if(pos[i]) s[i] = s[i] - mn + mx, m = max(m, s[i]);

	m++;

	build_sa();

	build_height();

	build_st();

	solve();

	printf("%d\n", ans + 1);

	return 0;

}