import sys
t=[]
for l in sys.stdin:t+=[l[:-1]]
m=[{} for i in range(len(t[0]))]
for l in t:
 i=0
 for c in l:
  if c in m[i]:m[i][c]+=1
  else:m[i][c]=1
  i+=1
r=""
for w in m:
 q=0
 for a in w:
  b=w[a] 
  if b>q:q=b;p=a
 r+=p
print(r)