#include#includeint k[10005];int main(){int i,d,n,m,c=0;while(scanf("%d%d",&n,&m)==2){memset(k,0,sizeof(k));for(i=0;i scanf("%d",&d); if(!k[d])c++; k[d]=1;}if(m==c)printf("YES\n");else printf("NO\n");}return 0;}/*BY TXJ*/突然发现不用排序