program ex;
var
f:array[1..2000000] of boolean;
b:array[1..5000] of double;
c:array[1..5000] of longint;
i,j,t,n:longint;

procedure init;
begin
  assign(input,'light.in');
  assign(output,'light.out');
  reset(input);
  rewrite(output);
  readln(n);
  for i:=1 to n do
  begin
    read(b[i]);
    readln(c[i]);
  end;
  close(input);
  for i:=1 to 2000000 do f[i]:=false;
end;

begin
  init;
  for i:=1 to n do
  begin
    for j:=1 to c[i] do
    begin
      t:=trunc(b[i]*j);
      if f[t] then f[t]:=false else f[t]:=true;
    end;
  end;
  for i:=1 to 2000000 do
  begin
    if f[i] then
    begin
      writeln(i);
      close(output);
      halt;
    end;
  end;
  close(output);
end.