{
TASK: gen
LANG: PASCAL
}

program gen;
var i,j,k:word;s1,s:string;
begin
readln(s1);

readln(k);
for i:=1 to k do readln(s);

readln(j);
for i:=1 to j do readln(s);

if s1 = 'aababb' then writeln('BC') else writeln(0);
end.