import sys

n,m=map(int,input().split())

a=list(map(int,input().split()))
b=list(map(int,input().split()))

for i in range(1,10):
    if i in a and i in b:
        print(i)
        exit(0)

x=min(a)
y=min(b)
sys.stdout.write('%d%d'%(min(x,y),max(x,y)))