#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <stack>
#include <algorithm>
using namespace std;
#define root 1,n,1
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define lr rt<<1
#define rr rt<<1|1
typedef long long LL;
typedef pair<int,int>pii;
#define X first
#define Y second
const int oo = 1e9+7;
const double PI = acos(-1.0);
const double eps = 1e-6 ;
const int N = 305 ;
const int mod = 1e9+7;
LL dp[N][N];
int n , m , a[N] , b[N] ;
void init() {
    memset( dp , 0 , sizeof dp );
    dp[0][0] = 1 ;
    for( int i = 1 ; i <= n ; ++i ) {
        for( int j = 0 ; j <= m ; ++j ){
            for( int k = a[i] ; k <= b[i] ; ++k ){
                if( j < k ) continue ;
                dp[i][j] += dp[i-1][j-k];
            }
        }
    }
}
void Run() {
    for( int i = 1 ; i <= n ; ++i ){
        cin >> a[i] >> b[i] ;
    }
    init(); cout << dp[n][m] << endl ;
}
int main()
{
    //freopen("in.txt","r",stdin);
    ios::sync_with_stdio(false);
    while( cin >> n >> m ) Run();
}