> #include <stdio.h>
> #include <stdlib.h>
> typedef struct node
> {
> 	int s;
> 	int e;
> }Node;
> Node p[1000010];
> int cmp(const void *_a,const void *_b)
> {
> 	Node *a=(Node*)_a;
> 	Node *b=(Node*)_b;
> 	if(a->s==b->s)
> 		return b->e-a->e;
> 	return a->s-b->s;
> }
> int main()
> {
> 	int n,t,i,j,f,c,mark,mx,k;
> 	while(scanf("%d %d",&n,&t)!=EOF)
> 	{
> 		for(i=0;i<n;i++)
> 		scanf("%d %d",&p[i].s,&p[i].e);
> 		qsort(p,n,sizeof(p[0]),cmp);
> 		if(p[0].s!=1)
> 		{
> 			printf("-1\n");
>             continue;
> 		}
> 		if(p[0].s==1&&p[0].e==t)
> 		{
> 			printf("1\n");
> 			continue;
> 		}
> 		c=1;
> 		f=0;
> 		for(i=0;i<n;)
> 		{
> 			mark=0;
> 			mx=p[i].e;
> 			for(j=i+1;j<n;j++)
> 			if(p[j].s>=p[i].s&&p[j].s<=p[i].e+1)
> 			{
> 				if(p[j].e>mx)
> 				{
> 					mx=p[j].e;
> 					k=j;
> 					mark=1;
> 				}
> 			}
> 			if(mark)
> 			{
> 				i=k;
> 				c++;
> 			}
> 			else
> 				break;
> 			if(p[i].e==t)
> 			{
> 				f=1;
> 				break;
> 			}
> 		}
> 		if(f)
> 			printf("%d\n",c);
> 		else
> 			printf("-1\n");
> 	}
> 	return 1;
> }
> 
> 
> 		
>