1 # include <iostream> 2 # include <cstdio> 3 # include <cstring> 4 # include <string> 5 # include <cmath> 6 # include <vector> 7 # include <map> 8 # include <queue> 9 # include <cstdlib>10 # include <algorithm>11 # define MAXN 100000112 using namespace std;13 14 inline int get_num() {15     int k = 0, f = 1;16     char c = getchar();17     for(; !isdigit(c); c = getchar()) if(c == ‘-‘) f = -1;18     for(; isdigit(c); c = getchar()) k = k * 10 + c - ‘0‘;19     return k * f;20 }21 22 int n, k, tot, sum, h, t, ans = 1 << 30;23 int num[MAXN];24 25 struct node26 {27     int a, pos;28 }p[MAXN];29 30 inline bool cmp(node x, node y)31 {32     return x.pos < y.pos;33 }34 35 int main()36 {37     int i, j, m;38     n = get_num();39     k = get_num();40     for(i = 1; i <= k; i++)41         for(j = 1, m = get_num(); j <= m; j++)42             p[++tot].a = i, p[tot].pos = get_num();43     sort(p + 1, p + n + 1, cmp);44     for(h = 1, t = 0; h <= n; h++)45     {46         while(sum < k && t < n)47         {48             if(!num[p[++t].a]) sum++;49             num[p[t].a]++;50         }51         if(sum == k) ans = min(ans, p[t].pos - p[h].pos);52         num[p[h].a]--;53         if(!num[p[h].a]) sum--;54     }55     printf("%d", ans);56     return 0;57 }