from copy import copy

N=int(input())
Y=[0]+list(map(int,input().split()))+[10**10]
D=copy(Y)

f=0
Z=[]
while Y!=Z:
    Z=copy(Y)
    t=0
    for i in range(1,N+2):
        if t==0 and Y[i-1]>Y[i]:
            t=1
            p=i-1
        elif t==1 and Y[i-1]<=Y[i]:
            t=0
            k=(p+i-1)//2
            for j in range(p,i):
                Y[j]=Y[k]

C=0
for i in range(1,N+1):
    C+=abs(D[i]-Y[i])

print(C)