var ans:array[1..20] of string;
    n,min,i,j:longint;
    a:array[1..20] of string;
    temp:array[1..20] of string;
    c:array['A'..'Z'] of longint;
    b:char;
 
procedure  put(k:longint);
var tc:array['A'..'Z'] of longint;
    t:array[1..20] of string;
    v:boolean;
    i:longint;
begin
if k=n+1 then // count to see if all 'A' to 'Z' are included and check for min number of word used
else
begin
inlucde word[k])
increase frequency of each letter in word(k)
check if 'a' to 'z' are included and check for min
if not put(k+1)
 
deduct frequency of word[k]
put (k+1)
 
 
end;
end;
 
 
 
 
 
 
begin
readln(n);
 
for b:='A' to 'Z' do
    c[b]:=0;
 
for i:=1 to n do
  begin
     readln(a[i]);
     for j:=1 to length(s[i]) do
         inc(c[s[i,j]])
  end;
 
for b:='A' to 'Z' do
  if c[b]=0 then
          begin
             writeln('Impossible');
             halt;
          end
  else
  begin
     min:=999;
     put(1);
  end;
 
 
readln;
end.

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