from heapq import heappush, heappop

n = int(input())
H = list(map(int,input().split()))
ans = 0

lis = []
for h in H:
    if lis and lis[0] < -h:
        l = -heappop(lis)
        ans += abs(l-h)
        heappush(lis,-h)
    heappush(lis,-h)
print(ans)