uva941測資B

Input:
20
dbe
4
abdc
20
adbc
20
abdge
101
abshi
30
adbshug
1000
abxycde
2000
akxyzpqw
10000
akxyznpqw
362879
akxyznpqwc
362879
abjqeprtmniz
279001608
abiqevzxprtmn
2000000078
abiqnvzxyeprtm
20000000788
abinvzxywqeprtc
200000007888
abcvzxywoiqeprtm
2000000078888
cbiqepzxywosrtmnv
20000000788888
ubiqxywosceprtmnvz
200000007888888
jbiqeposcdrtmnvzxyw
20000000788888888
abcdenopqrstfghijkyz
2432902008176620000
abcyzlmnopqrstefghij
1232902008176610000
Output:
ebd
dbac
dbac
gaedb
bhais
bgdsuah
cxebday
kzypwxaq
zyxwqpnka
azyxwqpnkc
nzrqmibjaept
mebirnqzpvtax
iexaqtybznmvpr
cnbtqwpxeyraivz
bqzeoiravtpcwxmy
bznpwrictsxovqyem
bsrziemxunyvqpcotw
edjynxwrpczoqtsmvbi
zytsrqponkjieacdghbf
mcoghjfznpbrlysaeiqt