func numJewelsInStones(_ J: String, _ S: String) -> Int {
    let jewels = Set(J)
    var count = 0

    for stone in S {
        if jewels.contains(stone) {
            count += 1
        }
    }
    return count
}

let num = numJewelsInStones("aA", "aAAbbbb")
print(num)