#include <iostream>

#include <algorithm>

#include <cstdio>

#include <math.h>

using namespace std;

struct Cow

{

    int b, e;

}cow[];

int cmp(Cow a, Cow b)

{

    return a.b < b.b;

}

int main()

{

    int n, t;

    int ans = , T = ;

    int i = ;

    scanf("%d%d", &n, &t);

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

        scanf("%d%d", &cow[i].b, &cow[i].e);

    sort(cow, cow + n, cmp);

    while (T<t&&i<n)

    {

        ans++;

        int end = T;

        if (cow[i].b > T + )

        {

            break;

        }

        else

        {

            while (i<n&&cow[i].b <= T + )

            {

                end = max(end, cow[i].e);

                i++;

            }

            T = end;

        }

        if (T >= t)

        {

            printf("%d\n", ans);

            return ;

        }

    }

    if (T >= t)

        printf("%d\n", ans);

    else

        printf("-1\n");

    return ;

}