program light;
var
  i,j,max,n,zt:longint;
  z:real;
  a:array[1..200000000] of real;
  b:array[1..200000000] of boolean;
  t:array[1..200000000] of integer;
begin
  assign(input,'light.in');
  assign(output,'light.out');
  reset(input);
  rewrite(output);
  readln(n);
  for i :=1 to n do
    readln(a[i],t[i]);
  max:=1;
  fillchar(b,sizeof(b),false);
  for i:=1 to n do
  begin
    for j:=1 to t[i] do
    begin
      z:=int(a[i]*j);
      zt:=trunc(z);
      if zt>max then max:=zt;
      b[zt]:=not(b[zt]);
    end;
  end;
  for i:=1 to max do
    if b[i] then begin
      writeln(i);
      break;
    end;
  close(input);
  close(output);
end.