#include <bits/stdc++.h>
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("Ofast,unroll-loops")
using namespace std;
#define pb push_back
#define int long long
#define f first
#define s second
#define pii pair<int,int>
const int mod= 1e9 +7;
const int N=2505;
vector<vector<int>> dist(N, vector<int> (N, mod));
void solve(){
int n,m,k;
cin>>n;
if(n<=2505){
vector<int>l(n+1),r(n+1);
for(int i = 0;i<n;i++){
int a,b;
cin>>l[i]>>r[i];
l[i]--;r[i]--;
}
int h,x;
cin>>h>>x;
x--;
priority_queue <pair<int,pii>, vector <pair<int,pii>>, greater <pair<int,pii>> > q;
q.push({1,{l[x],r[x]}});
dist[l[x]][r[x]] = 1;
int ml = -1,mr = -1;
while(!q.empty()){
auto [w,t] = q.top();
int x = t.f,y = t.s;
q.pop();
if(dist[x][y]<w)continue;
int ml = x;int mr = y;
for(int i = x;i<=y;i++){
ml = min(ml,l[i]);
mr = max(mr,r[i]);
}
if(x<y){
if(dist[ml][y]>dist[x][y] + 1){
dist[ml][y] = dist[x][y] + 1;
q.push({dist[ml][y],{ml,y}});
}
if(dist[x][mr]>dist[x][y] + 1){
dist[x][mr] = dist[x][y] + 1;
q.push({dist[x][mr],{x,mr}});
}
if(dist[x+1][y-1]>dist[x][y]){
dist[x+1][y-1] = dist[x][y];
q.push({dist[x+1][y-1],{x+1,y-1}});
}
// dist[x][mr] = dist[x][y] + 1;
}
else if(x==y){
if(dist[l[x]][r[x]]>dist[x][y] + 1){
dist[l[x]][r[x]] = dist[x][y] + 1;
q.push({dist[l[x]][r[x]],{l[x],r[x]}});
}
}
}
if(dist[0][n-1]==mod)cout<<-1<<"\n";
else cout<<dist[0][n-1]<<"\n";
}
else{
vector<pii>v;vector<int>pref(n+1,0);
int r1 = 1;
int cnt = 1;
for(int i = 0;i<n;i++){
int l,r;
cin>>l>>r;
v.pb({l,r});
if(i==0)r1 = r;
if(i==n)cout<<"Baiysh want a rulet!!!!!!!!!!!!!!!!!!!!!!\n";
else{
pref[i+1] = max(pref[i],r);
}
}
int last = -1;int ans = 1;
while(r1!=n){
last = r1;
r1 = pref[r1];
ans++;
if(last==r1){
cout<<-1<<"\n";
exit(0);
}
}
cout<<ans<<"\n";
}
}
signed main()
{
// freopen("seq.in", "r", stdin);
// freopen("seq.out", "w", stdout);
ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);
int cnt=0;
int tt=1;
while(tt--)solve();
}
