#include <bits/stdc++.h>
using namespace std;
#define append push_back
#define int long long
const int N=2e5+10,LG=17;
int mod=998244353;
int tree[N<<3];
void upd(int l,int r,int s,int a,int b){
if(r<a or l>a) return;
if(l==r){
tree[s]=min(tree[s],b);
return;
}
int m=(l+r)>>1;
upd(l,m,s*2,a,b);
upd(m+1,r,s*2+1,a,b);
tree[s]=min(tree[s*2],tree[s*2+1]);
}
int get(int l,int r,int s,int a,int b){
if(r<a or l>b) return 1e18;
if(a<=l and r<=b) return tree[s];
int m=(l+r)>>1;
return min(get(l,m,s*2,a,b),get(m+1,r,s*2+1,a,b));
}
void solve(int tst){
int n,m;
cin>>n>>m;
vector<pair<int,int>>v={{0,0}};
for(int i=1;i<=n;i++){
int a,b;
cin>>a>>b;
v.append({a,b});
}
vector<pair<int,int>>t;
for(int i=1;i<=n;i++){
t.append({v[i].first,i});
t.append({v[i].second,i+n});
}
t.append({0,0});
t.append({m,1e18});
sort(t.begin(),t.end());
int cnt=1;
for(int i=1;i<t.size();i++){
if(t[i].first!=t[i-1].first) cnt++;
int j=t[i].second;
if(j and j<=n){
v[j].first=cnt;
}
if(j>n and j!=1e18){
v[j-n].second=cnt;
}
}
sort(v.begin(),v.end());
int ans=1e18;
for(int X=1;X<=n;X++){
for(int i=1;i<=cnt*4;i++) tree[i]=1e18;
upd(1,cnt,1,v[X].first,0);
for(int i=X;i<=n;i++){
int x=1e18;
if(v[i].first<v[i].second) x=get(1,cnt,1,v[i].first,v[i].second);
else x=min(get(1,cnt,1,v[i].first,cnt),get(1,cnt,1,1,min(v[X].first-1,v[i].second)));
upd(1,cnt,1,v[i].second,x+1);
if(v[i].second<v[i].first and v[i].second>=v[X].first) ans=min(ans,x+1);
}
for(int i=1;i<X;i++){
int x=1e18;
if(v[i].first<v[i].second) x=get(1,cnt,1,v[i].first,v[i].second);
else x=min(get(1,cnt,1,v[i].first,cnt),get(1,cnt,1,1,min(v[X].first-1,v[i].second)));
upd(1,cnt,1,v[i].second,x+1);
if(v[i].second<v[i].first and v[i].second>=v[X].first) ans=min(ans,x+1);
}
}
if(ans==1e18) ans=-1;
cout<<ans<<endl;
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int t = 1;
// cin >> t;
for (int i = 0; i < t; i++) {
solve(i);
}
}
