program xxx;
var
x,x1,x2,x3,x4,x5,num:integer;
begin
readln(num);
x:=num;
x1:=num div 10000;
num:=num mod 10000;
x2:=num div 1000;
num:=num mod 1000;
x3:=num div 100;
num:=num mod 100;
x4:=num div 10;
x5:=num mod 10;
if x3=x4+x5 then writeln(x)
 else writeln(x4+x5);
end.

program reshef ;
var N, Last_Two : integer ;
begin
  writeln ('הכנס מספר בעל 5 ספרות:');
  readln (N);
  Last_Two := N mod 10 + N mod 100 div 10 ;
  If (N div 100 mod 10 = Last_Two) then writeln (N)
                                    else writeln (Last_Two);
end.