B = input()
N = input()
C = [int(raw_input()) for _ in xrange(N)]
avg = sum(C)/N+1
amari, tarinai = 0, float('inf')
if all(C[0]==c for c in C):
    print 0
    exit()
while amari+B < tarinai:
    amari = sum(c-avg for c in C if c > avg)
    tarinai = sum(avg-c for c in C if c < avg)
    avg -= 1
print amari+tarinai