program light;
var i,n:integer;
  a:extended; j,t,k,max:longint;
  L:array[1..2000000000] of 0..1;
begin
  assign(input,'light.in'); reset(input);
  assign(output,'light.out'); rewrite(output);
  readln(n);
  max:=0;
  for i:=1 to n do
  begin
    readln(a,t);
    for j:=1 to t do
    begin
      k:=trunc(a*j);
      if k>max then max:=k;
      L[k]:=1-L[k];
    end;
  end;
  for i:=1 to max do
    if L[i]=1 then
      begin writeln(i); break; end;
  close(input); close(output);
end.