#!/usr/local/bin/python3
N = int(input())
A = list(map(int, input().split()))[::-1]

ans = 0
while N != 0:
    m = max(A)
    idx = A.index(m) + 1
    ans += (len(A[:idx]) * m) - sum(A[:idx])
    A = A[idx:]
    N -= idx

print(ans)
