def main():
    B = int(input())
    N = int(input())
    C = [0] * N
    for i in range(N):
        C[i] = int(input())
    ans = 10**10
    for i in range(N):
        r = C[i]
        dif = 0
        summ = 0
        for j in range(N):
            if i == j:
                continue
            dif += C[j] - r
            summ += abs(C[j] - r)
        dif = 0-dif
        if B - dif >= 0:
            ans = min(ans, summ)
        else:
            a = ((abs(B-dif)+N-1)//N)
            if min(C) + a >= 0:
                ans = min(ans, summ+a*N)
        #print(ans, i, dif, summ, ((B+dif+N-1)//N))
    print(ans)

if __name__ == '__main__':
    main()