import sys
input = sys.stdin.readline

from heapq import heappop,heappush

N=int(input())
A=list(map(int,input().split()))

A.sort()
for i in range(N):
    A[i]-=i

L=[10**18]
R=[10**18]

MIN=0

for a in A:
    heappush(R,a)
    x=heappop(R)
    MIN+=abs(x-a)
    heappush(L,-x)

    heappush(L,-a)
    x=-heappop(L)
    heappush(R,x)
    MIN+=abs(x-a)

    R=[10**18]

print(MIN)