C++ Armstrong Number

#include<iostream>
using namespace std;
int main()
{
    int n, a, s = 0, r;

    cout << "Enter A Number : ";
    cin >> n;
    cout << endl;

    a = n;

    while(n != 0)
    {
        r = n % 10;
        s = s + (r * r * r);
        n = n / 10;
    }

    if(a == s)
    {
        cout << "It's a Armstrong Number.\n";
    }

    else
    {
        cout << "It's not a Armstrong Number.\n";
    }

    return 0;
}