class Happy
{ 
static int numSquareSum(int n) 
{ 
    int squareSum = 0; 
    while (n!= 0) 
    { 
        squareSum += (n % 10) * (n % 10); 
        n /= 10; 
    } 
    return squareSum; 
} 
   
//  method return true if n is Happy number 
static boolean isHappynumber(int n) 
{ 
    int slow, fast; 
    slow = fast = n; 
    do
    { 
        slow = numSquareSum(slow); 
   
        fast = numSquareSum(numSquareSum(fast)); 
   
    } 
    while (slow != fast); 
   

    return (slow == 1); 
} 
   
public static void main(String[] args) 
{ 
    int n = 13; 
    if (isHappynumber(n)) 
        System.out.println(n +  
        " is a Happy number"); 
    else
        System.out.println(n +  
        " is not a Happy number"); 
} 
} 
