#include <bits/stdc++.h>

using namespace std;

#define N 100005

bool cmp(pair<int,int> a,pair<int,int> b){

    if(a.first != b.first){

        return a.first < b.first;

    }else{

        return a.second <= b.second;

    }

}

int n,x,y;

pair<int,int> p[N];

int main(){

    cin>>n;

    cin>>x>>y;

    for(int i=0;i<n;i++)

        cin>>p[i].first>>p[i].second;

    sort(p,p+n,cmp);

    int i=0,ans=0;

    while(x<y){

        int temp=i;

        while(i<n && p[i].first <= x){

            if(p[i].second > p[temp].second) temp=i;

            i++;

        }

        if(p[temp].first > x || (i>=n && p[temp].second < x)) {

            cout<<"-1";

            return 0;

        }

        ans++;

        x=p[temp].second;

    }

    cout<<ans;

}