import Foundation

func solution(_ nums:[Int]) -> Int {
    guard let MAX = nums.max() else { return -1 }
    
    let maxLimit: Int = 3 * MAX - 3
    
    var isPrime: [Bool] = Array(repeating: true, count: maxLimit + 1)
    isPrime[0] = false
    isPrime[1] = false

    for n in 2...Int(sqrt(Double(maxLimit))) {
        if isPrime[n] {
            for i in stride(from: n * 2, through: maxLimit, by: n) {
                isPrime[i] = false
            }
        }
    }
    
    var ans: Int = 0
    let count: Int = nums.count

    for i in 0 ..< count - 2 {
        for j in i+1 ..< count - 1 {
            for k in j+1 ..< count {
                let sum: Int = nums[i] + nums[j] + nums[k]
                if isPrime[sum] {
                    ans += 1
                }
            }
        }
    }
    
    return ans
}

let nums: [Int] = [1,2,7,6,4]
print(solution(nums))