{
TASK:SEKA
LANG:PASCAL
}

program seka;
  { 15 olimpiada, I etapas, Jaunesniøjø grupë, 282 uþdavinys }
  var n, s1, s2, suma: integer;
begin
  readln (n);
  read (s1, s2);
  suma := s1 + s2;
  n := n - 2;
  while n > 0 do
    begin
      read (s1, s2);
      n := n - 2;
      if suma < s1 + s2
         then suma := s1 + s2;
    end;
  writeln (suma);  
end.
