  sx,sy=map(int,input().split())
  sn=list(map(int,input().split()))
  sn=sorted(sn)
  st,i=0,0
  flag=0
  while i<len(sn)-2:
    a,b,c=sn[i:i+3]
   for j in range(0,sy):
      a,b,c=a+1,b+1,c+1 
      if a<=5 and b<=5 and c<=5:
        flag=1
      else:
        flag=0
     if flag==1:
     st+=1
    i+=3
     a,b,c=0,0,0
  print(st)
