/BANK - Xếp hàng gửi tiền

              Uses Crt,math;
      Var n:longint;
          i,kq,j:longint;
          a,t,dp:array[-100..100000] of longint;
      Procedure Sort(l,r:longint);
      var i,j,x,temp:longint;
      begin
          i:=l; j:=r; x:=t[(l+r) div 2];
          repeat
               while t[i]<x do inc(i); while t[j]>x do dec(j);
               if i<=j then
                begin
                    temp:=a[j]; a[j]:=a[i]; a[i]:=temp;
                    temp:=t[j]; t[j]:=t[i]; t[i]:=temp;
                    inc(i); dec(j);
                end;
          until i>j;
          if l<j then sort(l,j); if i<r then sort(i,r);
      end;
      Begin
          readln(n);
          for i:=1 to n do
           begin
               readln(a[i],t[i]);
           end;
          Sort(1,n);
          //for i:=1 to n do writeln(a[i],' ',t[i]);
          kq:=-maxlongint;
          for i:=1 to n do
           begin
               for j:=t[i] downto 0 do
                begin
                    dp[j]:=max(dp[j],dp[j-1]+a[i]);
                    kq:=max(kq,dp[j]);
                end;
           end;
          writeln(kq);
          readln;
      End.