#include<stdio.h>

 #include<string.h>

 #include<algorithm>

 using namespace std;

 int dp[];

 struct Node

 {

     int xishouliang;

     int xingfuzhi;

 } a[];

 int main()

 {

     int i, j, t, m;

     while(~scanf("%d", &t))

     {

         memset(dp,,sizeof(dp));

         for (i = ; i <= t; i++)

             scanf("%d%d", &a[i].xingfuzhi, &a[i].xishouliang);

             scanf("%d",&m);

         for (i = ; i <= t; i++)

         {

             for (j = a[i].xishouliang; j <= m; j++)

             {

                 dp[j] = max(dp[j], dp[j - a[i].xishouliang] + a[i].xingfuzhi);

             }

         }

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

     }

     return ;

 }