CodeForces 615A Bulbs (水。）

H - Bulbs
Time Limit:1000MS     Memory Limit:262144KB     64bit IO Format:%I64d
& %I64u
Submit Status

Description

Vasya wants to turn on Christmas lights consisting of m bulbs. Initially, all bulbs are turned off. There are n buttons, each
of them is connected to some set of bulbs. Vasya can press any of these buttons. When the button is pressed, it turns on all the bulbs it's connected to. Can Vasya light up all the bulbs?

If Vasya presses the button such that some bulbs connected to it are already turned on, they do not change their state, i.e. remain turned on.

Input

The first line of the input contains integers n and m (1 ≤ n, m ≤ 100) —
the number of buttons and the number of bulbs respectively.

Each of the next n lines contains xi (0 ≤ xi ≤ m) —
the number of bulbs that are turned on by the i-th button, and then xi numbers yij (1 ≤ yij ≤ m) —
the numbers of these bulbs.

Output

If it's possible to turn on all m bulbs print "YES", otherwise print "NO".

Sample Input

Input

3 4
2 1 4
3 1 3 1
1 2

Output

YES

Input

3 3
1 1
1 2
1 1

Output

NO

Hint

In the first sample you can press each button once and turn on all the bulbs. In the 2 sample it is impossible to turn on the 3-rd lamp.

题意：有N个灯泡，分别由一些开关相连，给出每个开关连接灯泡的编号，问把这些开关全打开，能否把所有的灯泡打开

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;
int main()
{
int n,m,i,j,k,l,a[110];
while(scanf("%d%d",&n,&m)!=EOF)
{
memset(a,0,sizeof(a));
for(i=0;i<n;i++)
{
scanf("%d",&k);
for(j=0;j<k;j++)
{
scanf("%d",&l);
a[l]++;
}
}
int flag=0;
for(i=1;i<=m;i++)
{
if(a[i]==0)
{
flag=1;
break;
}
}
if(flag==0)
printf("YES\n");
else
printf("NO\n");
}
return 0;
}