/**
 * Tittle:	10154 - Weights and Measures
 * Author:	Cheng-Shih, Wong
 * Date:	2015/04/14
 */

// include files
#include <bits/stdc++.h>

using namespace std;

// definitions
#define FOR(i,a,b) for( int i=(a),_n=(b); i<=_n; ++i )
#define clr(x,v) memset( x, v, sizeof(x) )
#define N 6000

class Turtle {
public:
	int w, s;

	Turtle( int _w=0, int _s=0 ): w(_w), s(_s) {}

	const bool operator<( const Turtle &op ) const {
		return s < op.s;
	}
};

typedef priority_queue<int> PQI;

// declarations
Turtle tt[N];
int n;
int allw;

// functions


// main function
int main( void )
{

	// input
	n = 0;

	while( scanf( "%d%d", &tt[n].w, &tt[n].s )==2 ) ++n;

	// solve
	sort( tt, tt+n );

	allw = 0;
	PQI pq;

	FOR( i, 0, n-1 ) {
		allw += tt[i].w;
		pq.push( tt[i].w );
		if( allw > tt[i].s ) {
			allw -= pq.top();
			pq.pop();
		}
	}

	// output
	printf( "%d\n", pq.size() );

	return 0;
}