C++ :

#define MAXN 150010UL

#define ll long long

#include <algorithm>
#include <cstdio>
#include <queue>

struct Point{
	ll t1,t2;
	friend bool operator < (Point a,Point b){return a.t1<b.t1;}
	inline void in(){scanf("%lld%lld",&t1,&t2);return;}
};

std::priority_queue<Point> que;
Point s[MAXN];
int n,i;
ll cur_time;

inline bool comp(Point a,Point b){return a.t2<b.t2;}

int main(){
	scanf("%d",&n);
	for(;i<n;i++) s[i].in();
	for(std::sort(s,s+n,comp),i=0;i<n;i++){
		if(cur_time+s[i].t1<=s[i].t2) que.push(s[i]),cur_time+=s[i].t1;
		else if(s[i].t1<=que.top().t1&&cur_time+s[i].t1-que.top().t1<=s[i].t2) cur_time+=s[i].t1-que.top().t1,que.pop(),que.push(s[i]);
	}
	printf("%d",que.size());
	return 0;
}