Happy Number

https://leetcode.com/problems/happy-number/

Code:
class Solution {
public boolean isHappy(int n) {
int result = n;
while (result != 1 && result != 4)
{
result = squareSum(result);
}

        return (result == 1);
    }
    
    public static int squareSum(int temp)
    {
        int sum = 0;
        while (temp > 0)
        {
            int rem = temp % 10;
            sum += (rem * rem);
            temp = temp / 10;
        }
        
        return sum;
    }
}

What does “result != 4” means? Why not only “result != 1”?

Why not apply the process to 4 and find out?