program t1(input,output);
 var
 n:integer;
 a:double;
 t,k:int64;   max,i,j:longint;
 data:array[1..2000000]of byte;
 begin
 assign(input,'light.in');
 assign(output,'lighht.out');
 reset(input);
 rewrite(output);
 readln(n);  max:=0;
 fillchar(data,sizeof(data),0);
 for i:= 1 to n do
  begin
  readln(a,t);
   for j:= 1 to t do
    begin
    k:=trunc(a*j);
    data[k]:= (data[k]+1) mod 2 ;
    if k > max then max:=k;
    end;
  end;
  close(input);
 for i:= 1 to max do
 if data[i]=1 then
  begin
  writeln(i);
  close(output);
  exit; end;
  end.