def Repeat(x): 
    _size = len(x) 
    repeated = [] 
    for i in range(_size): 
        k = i + 1
        for j in range(k, _size): 
            if x[i] == x[j] and x[i] not in repeated: 
                repeated.append(x[i]) 
    return repeated 
list1 = [10, 20, 30, 20, 20, 30, 40,  
         50, -20, 60, 60, -20, -20] 
print(Repeat(list1))