package q762

var isPrime = [21]bool{}

func init() {
	for _, n := range []int{
		2, 3, 5, 7, 11, 13, 17, 19,
	} {
		isPrime[n] = true
	}
}

func count1s(n int) int {
	cnt := 0
	for n > 0 {
		if n%2 == 1 {
			cnt++
		}
		n >>= 1
	}
	return cnt
}

func countPrimeSetBits(left, right int) int {
	cnt := 0
	for n := left; n <= right; n++ {
		if isPrime[count1s(n)] {
			cnt++
		}
	}
	return cnt
}

var _ = countPrimeSetBits