func fairRations(B: [Int]) -> String {
    // Write your code here
    var oddIndex: [Int] = [Int]()
    var oddDict: [Int: Int] = [:]
    var steps: Int = 0
    
    for index in 0 ... B.count - 1 {
        if B[index] % 2 == 1 {
            oddIndex.append(index)
            oddDict[index] = index
        }
    }
    
    if oddIndex.count % 2 == 1 { return "NO" }    
    
    while(oddIndex.count > 1) {
      var currentOddIndex: Int = oddIndex.first!
      steps += 2
      let nextOddIndex: Int = currentOddIndex + 1
        if oddDict[nextOddIndex] == nil {
            oddIndex[0] = nextOddIndex
            oddDict.removeValue(forKey: currentOddIndex)
            oddDict[nextOddIndex] = nextOddIndex
            continue
        }
          
        while(currentOddIndex <= nextOddIndex) {
            oddIndex.removeFirst()
            oddDict.removeValue(forKey: currentOddIndex)
            currentOddIndex += 1
        }
    }
        
    return String(steps)
}