def median(x):
    N = len(x)
    if N % 2 == 1:
        return x[N//2]
    else:
        return (x[N//2-1] + x[N//2]) // 2

B = int(input())
N = int(input())
C = [int(input()) for _ in range(N)]
C = list(sorted(C))
med = median(C)

if B + sum(C) >= med * N:
    ans = sum(abs(C_i - med) for C_i in C)
    print(ans)
else:
    ave = (B + sum(C)) // N
    ans = sum(abs(C_i - ave) for C_i in C)
    print(ans)