         
         let s1 = DispatchSemaphore(value: 0)
         let s2 = DispatchSemaphore(value: 0)
-        let queue = DispatchQueue.global()
+        let queue = DispatchQueue.global(priority: .default)
         let group = DispatchGroup()
         
         queue.async(group: group) {

        
        let s1 = DispatchSemaphore(value: 0)
        let s2 = DispatchSemaphore(value: 0)
        let queue = DispatchQueue.global()
        let group = DispatchGroup()
        
        queue.async(group: group) {

        
        let s1 = DispatchSemaphore(value: 0)
        let s2 = DispatchSemaphore(value: 0)
        let queue = DispatchQueue.global(priority: .default)
        let group = DispatchGroup()
        
        queue.async(group: group) {
