2839번 '설탕 배달'

let input = Int(readLine()!)!
var array = [Int]()
let maxFive = input / 5
for countFive in 0...maxFive{
    var value = input
    value -= (countFive * 5)
    let countThree = value / 3
    value -= (countThree * 3)
    if(value != 0){
        array.append(-1)
    }
    else{
        array.append(countThree + countFive)
    }
}
array = array.filter { $0 != -1 }
if(array.count == 0){
    print("-1")
}
else{
    print(array.min()!)
}