package primes

// DecimalPeriod tries to find the decimal period (repetition) of the decimals of 1/n. Panics if n is not a prime number.
func DecimalPeriod(n int) int {
	return DecimalPeriod64(int64(n))
}

// DecimalPeriod64 tries to find the decimal period (repetition) of the decimals of 1/n. Panics if n is not a prime number.
func DecimalPeriod64(n int64) int {
	if !primes.IsPrime(n) {
		panic("not a prime")
	}
	if n <= 5 {
		return 1
	}
	length := 1
	a := int64(1)
	for a > 0 {
		a = (10*a + 1) % n
		length++
	}
	return length
}