//STATUS:C++_AC_31MS_388KB

 #include <functional>

 #include <algorithm>

 #include <iostream>

 //#include <ext/rope>

 #include <fstream>

 #include <sstream>

 #include <iomanip>

 #include <numeric>

 #include <cstring>

 #include <cassert>

 #include <cstdio>

 #include <string>

 #include <vector>

 #include <bitset>

 #include <queue>

 #include <stack>

 #include <cmath>

 #include <ctime>

 #include <list>

 #include <set>

 #include <map>

 using namespace std;

 #pragma comment(linker,"/STACK:102400000,102400000")

 //using namespace __gnu_cxx;

 //define

 #define pii pair<int,int>

 #define mem(a,b) memset(a,b,sizeof(a))

 #define lson l,mid,rt<<1

 #define rson mid+1,r,rt<<1|1

 #define PI acos(-1.0)

 //typedef

 typedef __int64 LL;

 typedef unsigned __int64 ULL;

 //const

 const int N=;

 const int INF=0x3f3f3f3f;

 const int MOD=,STA=;

 const LL LNF=1LL<<;

 const double EPS=1e-;

 const double OO=1e60;

 const int dx[]={-,,,};

 const int dy[]={,,,-};

 const int day[]={,,,,,,,,,,,,};

 //Daily Use ...

 inline int sign(double x){return (x>EPS)-(x<-EPS);}

 template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;}

 template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}

 template<class T> inline T lcm(T a,T b,T d){return a/d*b;}

 template<class T> inline T Min(T a,T b){return a<b?a:b;}

 template<class T> inline T Max(T a,T b){return a>b?a:b;}

 template<class T> inline T Min(T a,T b,T c){return min(min(a, b),c);}

 template<class T> inline T Max(T a,T b,T c){return max(max(a, b),c);}

 template<class T> inline T Min(T a,T b,T c,T d){return min(min(a, b),min(c,d));}

 template<class T> inline T Max(T a,T b,T c,T d){return max(max(a, b),max(c,d));}

 //End

 int n;

 int g[N][N],color[N];

 vector<int> G[N];

 bool bipartite(int u)

 {

     for(int i=;i<G[u].size();i++){

         int v=G[u][i];

         if(color[v]==color[u])return false;

         if(!color[v]){

             color[v]=-color[u];

             if(!bipartite(v))return false;

         }

     }

     return true;

 }

 int main(){

  //   freopen("in.txt","r",stdin);

     int i,j,a,b;

     while(~scanf("%d",&n))

     {

         mem(g,);

         for(i=;i<=n;i++)G[i].clear();

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

             while(scanf("%d",&a) && a)g[i][a]=;

         }

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

             for(j=i+;j<=n;j++){

                 if( (!g[i][j]&&g[j][i]) || (g[i][j]&&!g[j][i]) || (!g[i][j]&&!g[j][i])) {

                     G[i].push_back(j);

                     G[j].push_back(i);

                 }

             }

         }

         mem(color,);

         int ok=;

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

             if(!color[i]){

                 color[i]=;

                 if(!bipartite(i)){

                     ok=;

                     break;

                 }

             }

         }

         printf("%s\n",ok?"YES":"NO");

     }

     return ;

 }