import sys

n = int(input())
list_a = [int(i) for i in input().split(" ")]
list_b = []
for index, num in enumerate(list_a):
    list_b += [index + 1] * num

# def find_subarrays(arr):
#     result = 0
#     for l in range(1, len(arr) + 1):
#         for start in range(0, len(arr)):
#             if start+1 <= len(arr):
#                 tp = tuple(arr[start:start+l])
#                 result += (max(tp) - min(tp))
#     return result
# print(find_subarrays(list_b))


def f2(arr):
    result = 0
    for p1 in range(0, len(arr)):
        for p2 in range(p1, len(arr)):
            if arr[p1] == arr[p2]:
                continue
            else:
                result += arr[p2] - arr[p1]
    return result
print(f2(list_b))