def quartiles(arr):
    # Sort the array
    arr.sort()
    
    n = len(arr)
    mid = n // 2
    
    # Calculate Q1 (first quartile)
    if n % 2 == 0:
        Q1 = quants(arr[:mid])
    if n % 2 != 0:
        Q1 = quants(arr[:mid])
    
    # Calculate Q2 (median)
    Q2 = quants(arr)
    
    # Calculate Q3 (third quartile)
    if n % 2 == 0:
        Q3 = quants(arr[mid:])
    else:
        Q3 = quants(arr[mid+1:])
    
    return [Q1, Q2, Q3]

def quants(a):
    n = len(a)
    mid = n // 2
    
    if n % 2 != 0:
        median = a[mid]
    else:
        median = (a[mid] + a[~mid]) / 2
        
    return round(median)