def isExistCompare(compare,record):
    for data in compare:
        if record == data:
            return True
    return False

def getCompare(arr):
    compare = []
    for idx in range(len(arr)):
        record = arr[idx]
        if idx == len(arr)-1:
            checkAr = isExistCompare(compare, record)
            if  checkAr:
                compare.append(record)
            break
        recordNext = arr[idx+1]
        if record == recordNext:
            compare.append(record)
            continue
        checkAr = isExistCompare(compare, record)
        if  checkAr:
            compare.append(record)
        
    return compare
    
def coupleMapping(comparedData):
    res = []
    counter = 1
    for idx in range(len(comparedData)):
        records = comparedData[idx]
        if idx == len(comparedData)-1:
            if records == comparedData[len(comparedData)-2]:
                counter +=1
                res.append({"count": counter-1, "records":records })
            break
        else:
            recordsNext = comparedData[idx+1]
            if records == recordsNext:
                counter+=1
            else:
                res.append({"count": counter, "records":records })
                counter = 1
    return res

def coupleCompare(mapping):
    couple = 0
    for idx in range(len(mapping)):
        record = mapping[idx]
        if record["count"] %2 ==0 :
            couple += int(record["count"]/2)
        else:
            couple += int((record["count"]-1)/2)
    return couple
               
def sockMerchant(n, ar):
    arr = sorted(ar)
    comparedData = getCompare(arr)
    mapping = coupleMapping(comparedData)
    couple = coupleCompare(mapping)
    return couple