program garcom;

var
   N, L, C: integer;
   ans: integer;
   i: integer;
begin
   readln(N);
   ans := 0;
   for i := 1 to N do begin
      readln(L, C);
      if L > C then begin
         ans := ans + C;
      end;
   end;
   writeln(ans);
end.