n, d = list(map(int, input().split()))
a = list(map(int, input().split()))
m = int(input())
a.sort()
if m <= n:
print(sum(a[:m]))
else:
print((sum(a) + (n - m) * d))
1555A - PizzaForces | 1607B - Odd Grasshopper |
1084A - The Fair Nut and Elevator | 1440B - Sum of Medians |
1032A - Kitchen Utensils | 1501B - Napoleon Cake |
1584B - Coloring Rectangles | 1562B - Scenes From a Memory |
1521A - Nastia and Nearly Good Numbers | 208. Implement Trie |
1605B - Reverse Sort | 1607C - Minimum Extraction |
1604B - XOR Specia-LIS-t | 1606B - Update Files |
1598B - Groups | 1602B - Divine Array |
1594B - Special Numbers | 1614A - Divan and a Store |
2085. Count Common Words With One Occurrence | 2089. Find Target Indices After Sorting Array |
2090. K Radius Subarray Averages | 2091. Removing Minimum and Maximum From Array |
6. Zigzag Conversion | 1612B - Special Permutation |
1481. Least Number of Unique Integers after K Removals | 1035. Uncrossed Lines |
328. Odd Even Linked List | 1219. Path with Maximum Gold |
1268. Search Suggestions System | 841. Keys and Rooms |