def calc(b):
	lc = sum(b - c for c in C if c < b)
	rc = sum(c - b for c in C if c >= b)
	return 10**10 if rc + B < lc else rc + lc
B = input()
N = input()
C = [input() for i in range(N)]
left = 0
right = 10**9 + 1
while right - left > 2:
	lmid = (left*2 + right)/3
	rmid = (left + right*2)/3
	if calc(lmid) <= calc(rmid):
		right = rmid
	else:
		left = lmid
print min(calc(left),calc((left+right)/2),calc(right))