from heapq import *


class SlopeTrick:
    def __init__(self):
        self.minf = 0
        self.inf = 1 << 60
        self.R = [self.inf]
        self.L = [self.inf]
        self.addr = 0
        self.addl = 0

    @property
    def min(self):
        return self.minf

    def get_min(self):
        return (self.minf, -self.L[0] + self.addl, self.R[0] + self.addr)

    # add f(x) = a
    def add(self, a):
        self.minf += a

    # add f(x) = max(0, x - a)
    def add_x_a(self, a):
        self.minf += max(0, -self.L[0] + self.addl - a)
        heappush(self.L, self.addl - a)
        heappush(self.R, -heappop(self.L) + self.addl - self.addr)

    # add f(x) = max(0, a - x)
    def add_a_x(self, a):
        self.minf += max(0, a - self.R[0] - self.addr)
        heappush(self.R, a - self.addr)
        heappush(self.L, -heappop(self.R) - self.addr + self.addl)

    # add f(x) = abs(x - a)
    def add_abs(self, a):
        self.add_a_x(a)
        self.add_x_a(a)

    def add_l(self, x):
        assert x <= 0
        self.addl += x

    def add_r(self, x):
        assert x >= 0
        self.addr += x


def solve(n, A):
    A.sort()
    for i in range(n):
        A[i] -= i
    st = SlopeTrick()
    for a in A:
        st.add_abs(a)
        while len(st.R) > 1:
            heappop(st.R)

    return st.min


if __name__ == "__main__":
    n = int(input())
    A = list(map(int, input().split()))
    print(solve(n, A))