/*
	Name: NOI.AC-cheers
	Author: Duduuuu
	Date: 21/04/24
	Description: 
*/
#include<bits/stdc++.h>
using namespace std;
int n,t;
struct camera{
	int l,r;
}c[100001];
bool cmp(camera a,camera b){
	if(a.l==b.l){
		return a.r>b.r;
	}else{
		return a.l<b.l;
	}
}
int solve(){
	if(c[1].l>0){
		return -1;
	}
	int ans=1;
	int nowfar =c[1].r;
	int maxright=c[1].r;
	if(nowfar>=t){
		return ans;
	}
	int i=2;
	while(true){
		for(;(i<=n&&c[i].l<=nowfar);i++){
			maxright=max(maxright,c[i].r);
		}
		if(maxright<=nowfar){
			return -1;
		}
		ans++;
		nowfar=maxright;
		if(nowfar>=t){
			return ans;
		}
	}
	return -1;
}
int main(){
	int tp;
	scanf("%d%d",&n,&t);
	for(int i=1;i<=n;i++){
		scanf("%d%d",&c[i].l,&c[i].r);
	}
	sort(c+1,c+n+1,cmp);
	tp = solve();
	printf("%d",tp);
	return 0;
}