N=int(raw_input())
M=[]
for loop in xrange(N):
	A=map(int,raw_input().split())
	M+=A
num1=0
num2=0
num3=0
num4=0
num5=0
num6=0
num7=0
num8=0
num9=0
num10=0

for i in xrange(3*N):
	if M[i]==1:
		num1+=1
	elif M[i]==2:
		num2+=1
	elif M[i]==3:
		num3+=1
	elif M[i]==4:
		num4+=1
	elif M[i]==5:
		num5+=1
	elif M[i]==6:
		num6+=1
	elif M[i]==7:
		num7+=1
	elif M[i]==8:
		num8+=1
	elif M[i]==9:
		num9+=1
	elif M[i]==10:
		num10+=1
Ans=num1/2+num2/2+num3/2+num4/2+num5/2+num6/2+num7/2+num8/2+num9/2+num10/2+(num1%2+num2%2+num3%2+num4%2+num5%2+num6%2+num7%2+num8%2+num9%2+num10%2)/4
print Ans