Fruit

详解见：http://bonniebbs.is-programmer.com/posts/40073.html

#include <iostream>
#include <cstring>
#define N 10005
using namespace std;

int main()
{
    int n, m, a, b, ans;
    int c1[N], c2[N];
    while(cin >> n >> m)
    {
        memset(c1, 0, sizeof(c1));
        memset(c2, 0, sizeof(c2));
        ans = 0;
        cin >> a >> b;
        for(int i=a; i<=b&i<=m; i++)
        {
            c1[i] = 1;
        }
        n--;
        while(n--)
        {
            cin >> a >> b;
            for(int i=0; i<=m; i++)
            {
                for(int j=a; j<=b; j++)
                {
                    if(i+j<=m) 
                    {
                        c2[i+j] += c1[i];
                    }
                }
            }
            for(int i=0; i<=m; i++)
            {
                c1[i] = c2[i];
                c2[i] = 0;
            }
        }
        cout << c1[m] << endl;
    }
    return 0;
}