237

def FindSymbol(l,s):
    for i in range(len(l)):
        for j in range(len(l[i])):
            if l[i][j]==s:
                l[i][j]=''
                return(l)


N,M=map(int,input().split())
l=[list(input()) for i in range(N)]
lw=[input() for i in range(M)]
for word in lw:
    for symb in word:
        l=FindSymbol(l,symb)

resstr=''

for word in l:
    for symb in word:
        if symb!='':
            resstr+=symb
a=list(resstr)
a.sort()
print("".join(a))