import sys
import math
db, ar = list(map(int, input().strip().split()))
y = list(map(int, input().strip().split()))
s = sum(y)
Z=0
a = 0
m = min(y)
b=0
if s < ar*db:
    print(math.ceil((ar*db-s)/db))
elif s == ar*db:
    print(0)
else:
    if min(y) > math.ceil((s-ar*db)/db):
        print(math.ceil((s-ar*db)/db))
    else:
        while s-b+m*len(y)> ar*db and len(y)>1:
            m= min(y)

            Z+=(m-1)
            for i in range(len(y)):
                y[i]-= (m-1)
            b+=(len(y)*(m-1))
            for i in range(y.count(1)):
                y.remove(1)
        while s-a-b > db*ar:
            for i in range(len(y)):
                if y[i] > 1:
                    y[i]-=1
                    a+=1
            Z+=1
        print(Z)

        


        
sys.stdout.close()