public func solution(_ A : inout [Int]) -> Int {
    var suspect = 1               // the lowest possible value
    var B = Array(Set(A))         // eliminate duplicates
    B.sort()                      // order the data
    for x in B {                  // enumerate
        if (x > 0) {              // only care about positive ints
            if (x != suspect) {   // expected int is missing
                return suspect    // eureka!
            }
            suspect = x+1         // expect the next highest int
        }
    }
    return suspect
}