#4
N = int(input())
A = [0]*55
B  =[0]*9

for i in range(N):
    S= int(input())
    A[S] = 1

for i in range(55):
    if A[i]==1:
        if i <=4:
            B[0]+=1
        elif i <=8:
            B[1]+=1
        elif i <=12:
            B[2]+=1
        elif i <=16:
            B[3]+=1
        elif i <=20:
            B[4]+=1
        elif i <=24:
            B[5]+=1
        elif i <=28:
            B[6]+=1
        elif i <=32:
            B[7]+=1
        elif i <=36:
            B[8]+=1
        elif i <=38:
            B[8]+=1
        elif i <=40:
            B[7]+=1
        elif i <=42:
            B[6]+=1
        elif i <=44:
            B[5]+=1
        elif i <=46:
            B[4]+=1
        elif i <=48:
           B[3]+=1
        elif i <=50:
            B[2]+=1
        elif i <=52:
            B[1]+=1
        elif i <=54:
            B[0]+=1
c = 0
q = 0
for i in B:
    if i == 6:
        c+=1
    elif c >q:
        q=c
        c=0
print (q)