B = int(input())
N = int(input())
C = [int(input()) for _ in range(N)]
S = sum(C)
C.sort()
if N == 1:
    print(0)
    exit()
M = (N + 1) // 2
X = C[M - 1]
if S + B < X * N:
    X = (S + B) // N
cnt = 0
for i in range(N):
    cnt += abs(C[i] - X)
print(cnt)