// yukicoder: No.198 キャンディー・ボックス２
// 2019.8.2 bal4u

#include <stdio.h>
#include <stdlib.h>

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in() {   // 非負整数の入力
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

#define ABS(x)  ((x)>=0?(x):-(x))
int N;
int c[12];
int cmp(const void *a, const void *b) { return *(int *)a - *(int *)b; }

int main()
{
	int B, i, a;
	long long ans, s;
	
	B = in(), N = in(), s = 0;
	for (i = 0; i < N; i++) c[i] = in(), s += c[i];
	qsort(c, N, sizeof(int), cmp);
	a = c[N/2], ans = 0;
	if ((long long)a*N > s+B) a = (s+B)/N;
	for (i = 0; i < N; i++) ans += ABS(c[i]-a);
	printf("%lld\n", ans);
	return 0;
}