include <bits/stdc++.h>

using namespace std; struct node{

int data;
int l,r;

}; node tr1[1005]; node tr2[1005]; int tree1[1005]; int tree2[1005]; int t=0,t1=0,m; int cur=0; bool cmp=0; int dfs(){

int x;
cin>>x;
if(x==-1){
	return -1;
}
int cnt=cur++;
tr1[cnt].data=x;
tr1[cnt].l=dfs();
tr1[cnt].r=dfs();
return cnt; 

} void dfs2(int root,int sum){

if(root==-1){
	if(sum==m){
		cmp=1;
	}
	return;
}
if(tr1[root].l==-1 && tr1[root].r==-1){
	tree1[t++]=tr1[root].data;
}
dfs2(tr1[root].l,sum+tr1[root].data);
dfs2(tr1[root].r,sum+tr1[root].data);
return;

} int main(){

int root1=dfs();
cin>>m;
dfs2(root1,0);
if(cmp){
	cout<<"yes"<<endl;
	return 0;
}else{
	cout<<"no"<<endl;
}
return 0;

}