1 #include <iostream>
2 #include <cstdio>
3 #include <cstdlib>
4 #include <cstring>
5 #include <cmath>
6 using namespace std;
7 #define FOR(i,a,b) for(int i=a;i<=b;i++)
8 #define MST(a,b) memset(a,b,sizeof(a))
9 #define MAXN 105
10 #define MAXM 1050
11 int n,m;
12 int totx,toty,x[MAXN],y[MAXN];
13 int f[2][MAXN][MAXM];
14 int a,b;
15 int main()
16 {
17
18 while (scanf("%d%d",&n,&m)!=EOF)
19 {
20 FOR(i,1,n)scanf("%d%d",&x[i],&y[i]);
21 scanf("%d%d",&a,&b);
22 MST(f[0],128);
23 totx=0;
24 toty=0;
25 f[0][0][0]=0;
26 FOR(i,1,n)
27 {
28 MST(f[i%2],128);
29 totx+=x[i];
30 FOR(j,0,i)
31 FOR(k,0,totx)
32 {
33 if(j-1>=0 && k-x[i]>=0 && f[(i+1)%2][j-1][k-x[i]]>=0)f[i%2][j][k]=f[(i+1)%2][j-1][k-x[i]]+y[i];
34 if(f[(i+1)%2][j][k]>=f[i%2][j][k])f[i%2][j][k]=f[(i+1)%2][j][k];
35 }
36 }
37 int ans=-1;
38 FOR(k,a,totx)
39 if(f[n%2][m][k]>=b && f[n%2][m][k]-b+k-a>ans)ans=f[n%2][m][k]-b+k-a;
40 printf("%d\n",ans);
41 }
42 }
