# 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;
}

HDU 2152 Fruit (母函数)