func main()
	var N: int :: cui@input().toInt(&)
	var _: [][]char :: cui@input().split(" ")
	var A: []int :: #[N]int
	for i(0, N - 1)
		do A[i] :: _[i].toInt(&)
	end for
	var ans: int :: 10000
	for l(0, N - 1)
		for c(l, N - 1)
			var r: int :: l + 2 * (c - l)
			if(r > N - 1)
				skip l
			end if
			do ans :: [ans, f(A, l, c)].min()
		end for
	end for
	do cui@print("\{ans}\n")
	func f(A: []int, left: int, center: int): int
		var right: int :: left + 2 * (center - left)
		var plus: int
		var minus: int
		for i(0, ^A - 1)
			if(i < left)
				do plus :+ A[i]
			elif(left <= i & i <= center)
				var targetVal: int :: i - left + 1
				if(A[i] > targetVal)
					do plus :+ A[i] - targetVal
				elif(A[i] < targetVal)
					do minus :+ targetVal - A[i]
				end if
			elif(center < i & i <= right)
				var targetVal: int :: right - i + 1
				if(A[i] > targetVal)
					do plus :+ A[i] - targetVal
				elif(A[i] < targetVal)
					do minus :+ targetVal - A[i]
				end if
			else
				do plus :+ A[i]
			end if
		end for
		if(plus >= minus)
			ret plus
		else
			ret 10000
		end if
	end func
end func