last q

from itertools import combinations

x=raw_input()
y=x.split()
N=int(y[0])
K=int(y[1])

z=raw_input()
Arr=z.split()
Main=[]
for i in Arr:
    Main.append(int(i))

combs=combinations(Main,K)
shortcombs=set(combs)

def xor(L):
    S=0
    for i in L:
        S=xor_of_nums(S,i)

    return S

def xor_of_nums(x,y):
    ans=0;
    i=0;
    while(x>0 or y>0):
        ans=ans+((x%10+y%10)%10)*(10**i)
        x=x/10
        y=y/10
        i=i+1
    return ans

max=0
for i in shortcombs:
    ans=xor(i)
    if(ans>max):
        max=ans
    if(ans==9):
        break

print(max)