#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#define N 1010000using 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;
}