uses crt;
var f:text; m:string; i,j,n,d:longint;
s:array[1..1000000]of string;
begin
clrscr;
assign(f,'ONLY.INP');reset(f);
while not(eof(f)) do
begin
inc(n); readln(f,s[n]);
end;
close(f);
assign(f,'ONLY.OUT');rewrite(f);
for i:=1 to n do
begin
d:=0;
for j:=1 to n do
if s[i]=s[j] then inc(d);
if d=1 then m:=s[i];
end;
writeln(f,m);
close(f);
end.