#### Keith Number

A
s
```package com.thealgorithms.maths;

import java.util.*;

class KeithNumber {

//user-defined function that checks if the given number is Keith or not
static boolean isKeith(int x) {
//List stores all the digits of the X
ArrayList<Integer> terms = new ArrayList<Integer>();
//n denotes the number of digits
int temp = x, n = 0;
//executes until the condition becomes false
while (temp > 0) {
//determines the last digit of the number and add it to the List
//removes the last digit
temp = temp / 10;
//increments the number of digits (n) by 1
n++;
}
//reverse the List
Collections.reverse(terms);
int next_term = 0, i = n;
//finds next term for the series
//loop executes until the condition returns true
while (next_term < x) {
next_term = 0;
//next term is the sum of previous n terms (it depends on number of digits the number has)
for (int j = 1; j <= n; j++) {
next_term = next_term + terms.get(i - j);
}
i++;
}
//when the control comes out of the while loop, there will be two conditions:
//either next_term will be equal to x or greater than x
//if equal, the given number is Keith, else not
return (next_term == x);
}

//driver code
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
if (isKeith(n)) {
System.out.println("Yes, the given number is a Keith number.");
} else {
System.out.println("No, the given number is not a Keith number.");
}
}
}
```  