import numpy as np
N = int(input())
A = list(map(int, input().split()))
B = A
A = np.array(A)
B = np.array(B)
emp = np.zeros(N)
Amax_ind = np.argmax(A)
emp[Amax_ind:] = max(A)
A[Amax_ind:] = 0
while True:
    subAmax_ind = np.argmax(A)
    emp[subAmax_ind:Amax_ind] = max(A)
    A[subAmax_ind:Amax_ind] = 0
    Amax_ind = subAmax_ind
    if 0 not in emp:
        break
print(int(sum(emp-B)))