WA on #11#15

#include<iostream>
#include<cstdio>
#include<algorithm>
#define int long long
using namespace std;
const int N=3e5+5;
struct Node
{
    int s,e;
};
Node a[N];
int cmp(Node a1,Node a2)
{
    if(a1.s==a2.s)
    {
        return a1.e>a2.e;
    }
    return a1.s<a2.s;
}
signed main(){
	//freopen("cleaning.in","r",stdin);
	//freopen("kkksc.out","w",stdout);
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
    int n,t;
    cin >> n >> t;
    for(int i=1;i<=n;i++)
    {
        cin >> a[i].s >> a[i].e;
    }
    sort(a+1,a+n+1,cmp);
    if(a[1].s>1)
    {
        cout << -1 << endl;
        return 0;
    }
    int r=a[1].e;
    int ans=1;
    for(int i=2;i<=n;i++)
    {
        int kkk=-1;
        for(int j=i;j<=n;j++)
        {
            if(a[j].s>r+1)
            {
                break;
            }
            kkk=max(kkk,a[j].e);
            i=j;
        }
        if(kkk<=r)
        {
            cout << -1;
            return 0;
        }
        r=kkk;
        ans++;
        if(r>=t)
        {
            break;
        }
    }
    if(r<t)
    {
        cout << -1;
        return 0;
    }
    cout << ans << endl;
	return 0;
}