B = int(input())
N = int(input())
C = [0] * N
for i in range(N):
    C[i] = int(input())
    B += C[i]
M = B//N
C.sort()
M = min(M, C[N//2])
ans = 0
for i in range(N):
    ans += abs(M - C[i])
print(ans)