func theGreatXor(x int64) int64 {
    if x & (x - 1) == 0 {
        return x - 1
    }
    var count uint
    var temp int64 = x
     
    for temp > 0 {
        temp = temp >> 1
        count++            
    }
    if count == 0{
        return 0
    } else{
        return 1 << (count - 1) - (x - (1 << (count - 1))) - 1    
    }

}