import sys

data=sys.stdin.read().split()
ptr=0
n=int(data[ptr])
ptr+=1
aList=list(map(int,data[ptr:]))
i=3
num=0
while i<n:
    bList=aList[i-3:i+1]
    aSet=set(bList)
    for x in aSet:
        if bList.count(x)==3:
            num+=1
            i+=3
            break
    i+=1
print(num)