Euler's Totient

$\varphi(n)$ counts the integers $1 \le k \le n$ with $\gcd(k, n) = 1$. Print $\varphi(n)$.

Use $\varphi(n) = n \prod_{p \mid n} \left(1 - \frac1p\right)$ over the distinct primes dividing $n$.

9

6

1

1