#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#include <queue>
#define rg register int
#define ll long long
#define RG register
#define il inline
using namespace std;

il int gi() {
  rg x=0,o=0;RG char ch=getchar();
  while(ch!=‘-‘&&(ch<‘0‘||‘9‘<ch)) ch=getchar();
  if(ch==‘-‘) o=1,ch=getchar();
  while(‘0‘<=ch&&ch<=‘9‘) x=(x<<1)+(x<<3)+ch-‘0‘,ch=getchar();
  return o?-x:x;
}

#define N 110
#define M 110
int n,m,K,C,ans;
int a[N],b[N],c[M],w[M],sum[M];
int f[N][M][M*20];

// 实际上就是只选 k 个物品的背包嘛 。。。

int main() {
  n=gi(),m=gi(),K=gi(),C=gi();
  for(rg i=1;i<=n;++i) a[i]=gi();
  for(rg i=1;i<=n;++i) b[i]=gi();
  for(rg p,q,i=1;i<=m;++i) {
    p=gi(),q=gi();
    w[i]=b[p]+b[q];
    c[i]=a[p]*a[q];
    sum[i]=sum[i-1]+w[i];
  }
  
#define Getmax(a,b) (a)=(a)>(b)?(a):(b)

  for(rg i=1;i<=m;++i)  
    for(rg j=1;j<=min(i,K);++j)
      for(rg l=sum[i];l>=0;--l){ 
    f[i][j][l]=f[i-1][j][l];
        if(l>=w[i]&&(f[i-1][j-1][l-w[i]]>0||l==w[i]))
      Getmax(f[i][j][l],f[i-1][j-1][l-w[i]]+c[i]);
    if(l>=C) Getmax(ans,f[i][j][l]);
      }

  ans?printf("%d",ans):puts("-1");
  return 0;
}