program zzn;
var
        v:array[1..50000000]of boolean;
        n,i,j,maxn,a:longint;
        t:double;
procedure init;
begin
        assign(input,'light.in');
        reset(input);
        assign(output,'light.out');
        rewrite(output);
        readln(n);
end;
procedure closef;
begin
        close(input);
        close(output);
end;
procedure main;
begin
        fillchar(v,sizeof(v),0);
        maxn:=0;
        for i:=1 to n do
        begin
             readln(t,a);
             if trunc(t*a)>maxn then maxn:=trunc(t*a);
             for j:=1 to a do
             begin
                 v[trunc(j*t)]:=not(v[trunc(j*t)]);
             end;
        end;
        for i:=1 to maxn do if v[i] then
         begin
             writeln(i);
             exit;
         end;
end;
begin
        init;
        main;
        closef;
end.