program light;
var
  a:array [1..5000] of double;
  t:array [1..5000] of longint;
  hash:array [1..20000000] of boolean;
  v,i,j,n:longint;
begin
  fillchar (a,sizeof(a),0);
  fillchar (hash,sizeof(hash),0);
  assign (input,'light.in');
  reset (input);
  readln (n);
  for i:=1 to n do begin
    readln (a[i],t[i]);
	for j:=1 to t[i] do begin
	  v:=trunc(a[i]*j);
	  hash[v]:=not(hash[v]);
	end;
  end;
  close (input);
  assign (output,'light.out');
  rewrite (output);
  i:=1;
  while hash[i]=false do inc(i);
  writeln (i);
  close (output);
end.