#include<bits/stdc++.h>
using namespace std;
long long read(){
    long long x=0,f=1;
    char ch=getchar();
    while(ch<'0'||ch>'9'){
        if(ch=='-')
            f=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9'){
        x=(x<<1)+(x<<3)+(ch^48);
        ch=getchar();
    }
    return x*f;
}
void write(long long x){
    if(x<0){
        putchar('-');
        x=-x;
    }
    if(x>9)write(x/10);
    putchar(x%10+'0');
}
long long n,h,a[100005],b[100005],maxn=-1,k=0,l=0;
priority_queue<int>q;
int main(){
	//freopen("1.txt","r",stdin);
	n=read(),h=read();
	for(int i=1;i<=n;i++){
		a[i]=read();
		b[i]=read();
	}
	for(int i=1;i<=n;i++){
		k+=a[i];
		q.push(a[i]);
		if(k>=h){
			k-=q.top();
			q.pop();
			l++;
		}
		k-=b[i];
	}
	cout<<l;
	return 0;
}