Problem:
Score : 700 points

Problem Statement

In the final of CODE FESTIVAL in some year, there are N participants.
The height and power of Participant i is H_i and P_i, respectively.

Ringo is hosting a game of stacking zabuton (cushions).

The participants will line up in a row in some order, and they will in turn try to add zabuton to the stack of zabuton.
Initially, the stack is empty.
When it is Participant i's turn, if there are H_i or less zabuton already stacked, he/she will add exactly P_i zabuton to the stack. Otherwise, he/she will give up and do nothing.

Ringo wants to maximize the number of participants who can add zabuton to the stack.
How many participants can add zabuton to the stack in the optimal order of participants?

Constraints

1 \leq N \leq 5000

0 \leq H_i \leq 10^9

1 \leq P_i \leq 10^9

Input

Input is given from Standard Input in the following format:

N
H_1 P_1
H_2 P_2
:
H_N P_N

Output

Print the maximum number of participants who can add zabuton to the stack.

Sample Input 1

3
0 2
1 3
3 4

Sample Output 1

2

When the participants line up in the same order as the input, Participants 1 and 3 will be able to add zabuton.

On the other hand, there is no order such that all three participants can add zabuton. Thus, the answer is 2.

Sample Input 2

3
2 4
3 1
4 1

Sample Output 2

3

When the participants line up in the order 2, 3, 1, all of them will be able to add zabuton.

Sample Input 3

10
1 3
8 4
8 3
9 1
6 4
2 3
4 2
9 2
8 3
0 1

Sample Output 3

5

Solution in Pascal (FPC 2.6.2) (judge verdict: Accepted)

{$R+,S+,Q+,I+,O-}
{R-,S-,Q-,I-,O+}
// Code By H~$~C

uses math;

type
  int32 = longint;
  double = extended;
  bool = boolean;

const inf = 1061109567;

var
  i, j, swap_tmp, x, y, z: int32;
  n, ans: int32;
  h, p: array [0 .. 5005] of int32;
  dp: array [0 .. 5005] of int64;

function qsort_less(i, j: int32): bool;
begin
  qsort_less := (h[i] + p[i]) < (h[j] + p[j]);
end;
procedure qsort_swap(i, j: int32);
  var _swap_tmp: int32;
begin
  _swap_tmp := h[i]; h[i] := h[j]; h[j] := _swap_tmp;
  _swap_tmp := p[i]; p[i] := p[j]; p[j] := _swap_tmp;
end;
procedure qsort(_l, _r: int32);
  var i, j, _p: int32;
begin
  if (_r = _l) then exit;
  i := _l; j := _r;
  _p := _l;
  repeat
    while qsort_less(i, _p) do inc(i);
    while qsort_less(_p, j) do dec(j);
    if (i <= j) then begin
      qsort_swap(i, j);
      inc(i); dec(j);
    end;
  until (i > j);
  if (i < _r) then qsort(i, _r);
  if (j > _l) then qsort(_l, j);
end;

begin
//  assign(input,'in'); reset(input);
//  assign(output,'1.out'); rewrite(output);
  randseed := 6714;
  
  readln(n);
  for i := 1 to n do begin
    readln(h[i], p[i]);
  end;
  qsort(1, n);
  
  fillchar(dp, sizeof(dp), 63);
  dp[0] := 0;
  for i := 1 to n do begin
    for j := i - 1 downto 0 do begin
      if (dp[j] <= h[i]) and (dp[j + 1] > dp[j] + p[i]) then begin
        dp[j + 1] := dp[j] + p[i];
      end;
    end;
  end;
  
  ans := 0;
  for i := 0 to n do begin
    if (dp[i] < 1000000000000000000) then begin
      ans := i;
    end;
  end;
  writeln(ans);
  
  close(input);
  close(output);
end.