# include<stdio.h>

# include <algorithm>

# include <string.h>

# include <iostream>

using namespace std;

int main()

{

    int n,m,i,j,k;

    int c1[110],c2[110];

    int a[110],b[110];

    while(~scanf("%d%d",&n,&m))

    {

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

            scanf("%d%d",&a[i],&b[i]);

        memset(c1,0,sizeof(c1));

        memset(c2,0,sizeof(c2));

        for(i=a[0];i<=b[0];i++)//第一种水果

            c1[i]=1;

        for(i=1;i<n;i++)

        {

            for(j=0;j<=m;j++)//买m种水果组成的拼盘

            {

                for(k=a[i];k<=b[i];k++)//i类水果数量 从a[]到b[]

                {

                    c2[j+k]+=c1[j];

                }

            }

            for(j=0;j<=m;j++)

            {

                c1[j]=c2[j];

                c2[j]=0;

            }

        }

        printf("%d\n",c1[m]);

    }

    return 0;

}