let inputCount = Int(readLine()!)!

var cnt = [Int:Int]()
var ans = 0
for i in 1...inputCount {
    let inpt = readLine()!.split(separator: " ").map{Int($0)!}
    for j in 0...inpt.count-1
    {
        if(cnt[inpt[j]]==nil) {
            cnt[inpt[j]] = 1
        } else {
            ans+=1
            cnt.removeValue(forKey:inpt[j])
        }
    }
}
ans+=cnt.count/4
print(ans)