Q.Let us write a pseudocode and draw a flowchart where multiple conditions are checked to categorise a person as either child (<13), teenager (>=13 but <20) or adult (>=20), based on age specified.

What Is an Armstrong Number? The Intuition

Imagine you have a number, say 153. Now take each of its digits — 1, 5, and 3 — and raise each one to a power equal to the total number of digits in the number. For 153, that's three digits, so you cube each digit:

$1^3 = 1$, $5^3 = 125$, $3^3 = 27$

Now add them up: $1 + 125 + 27 = 153$. You get back exactly the number you started with. That's the core idea: a number that equals the sum of its own digits, each raised to the power of the number of digits.

That self-referential property is what makes a number an Armstrong number (also called a narcissistic number or pluperfect digital invariant).

The Precise Definition

In plain language: write the number, count how many digits it has (call that $d$), raise each digit to the $d$-th power, sum those powers, and check if the sum equals the original number.

Examples to Build Understanding

Three-digit case (the classic):

• 153: $1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153$ → Armstrong
• 370: $3^3 + 7^3 + 0^3 = 27 + 343 + 0 = 370$ → Armstrong
• 371: $3^3 + 7^3 + 1^3 = 27 + 343 + 1 = 371$ → Armstrong
• 407: $4^3 + 0^3 + 7^3 = 64 + 0 + 343 = 407$ → Armstrong

Four-digit example:

• 1634: $1^4 + 6^4 + 3^4 + 4^4 = 1 + 1296 + 81 + 256 = 1634$ → Armstrong

A non-example:

• 123: $1^3 + 2^3 + 3^3 = 1 + 8 + 27 = 36$, not 123 → not Armstrong

Single-Digit Numbers: A Special Case

Every single-digit number (1 through 9) is trivially an Armstrong number. Why? A one-digit number has $d = 1$, and any digit raised to the power 1 is itself. So $5^1 = 5$, and the sum is just 5. This matches the definition perfectly.

How to Check Any Number (The Algorithm)

To decide if a number $n$ is an Armstrong number:

1. Count the digits of $n$. Call this $d$.
2. Extract each digit of $n$ one by one. …