合成数列の和 (Swift)

合成数列の和	https://qiita.com/advent-calendar/2018/composite-number
Python(/Ruby)	https://qiita.com/cielavenir/items/dcbd839b0c66af1bc971
Crystal	https://qiita.com/cielavenir/items/1a0dd1a94aca9935f5aa
Kuin	https://qiita.com/cielavenir/items/47fd18fc68055d990599
Swift	https://qiita.com/cielavenir/items/6cde3b20866c842dc9e2
Kotlin	https://qiita.com/cielavenir/items/f58eaa30f90781229a6d
Pascal	https://qiita.com/cielavenir/items/35c2fc54ca16b620c9c7

composite.swift

func isqrt(_ n: Int) -> Int {
	if n<=0 {return 0}
	if n<4 {return 1}
	var x=0
	var y=n
	while x != y && x+1 != y {x=y;y=(n/y+y)/2}
	return x
}

func isPrime(_ i: Int) -> Bool {
	if i<2 {
		return false
	}
	for j in 2...isqrt(i) {
		if i%j<1 {
			return false
		}
	}
	return true
}
var n=Int(readLine()!)!
var i=4
var s=0
var cnt=0
while cnt<n {
	if !isPrime(i) {
		s+=i
		cnt+=1
	}
	i+=1
}
print(s)