package main

import (
	"fmt"
)

func isHappy(n int) bool {
	if n < 11 {
		return n == 1 || n == 7 || n == 10
	}

	var number int
	for n > 0 {
		number += (n % 10) * (n % 10)
		n /= 10
	}

	return isHappy(number)
}

func main() {
	fmt.Println(isHappy(2))
	fmt.Println(isHappy(7))
	fmt.Println(isHappy(10))
	fmt.Println(isHappy(19))
}