import sys
import math
import bisect
from heapq import heapify, heappop, heappush
from collections import deque, defaultdict, Counter
from functools import lru_cache
from itertools import accumulate, combinations, permutations, product

sys.setrecursionlimit(1000000)
MOD = 10 ** 9 + 7
MOD99 = 998244353

input = lambda: sys.stdin.readline().strip()
NI = lambda: int(input())
NMI = lambda: map(int, input().split())
NLI = lambda: list(NMI())
SI = lambda: input()
SMI = lambda: input().split()
SLI = lambda: list(SMI())
EI = lambda m: [NLI() for _ in range(m)]


def main():
    B = NI()
    N = NI()
    C = sorted([NI() for _ in range(N)], reverse=True)
    m = C[::-1][(N-1)//2]
    ans = 0
    # print(m, C)
    for c in C:
        if c >= m:
            ans += c-m
            B += c-m
        else:
            if B >= m-c:
                B -= m-c
                ans += m-c
            else:
                ans += B
                B = 0
    print(ans)


if __name__ == "__main__":
    main()