#include<iostream>
#include<cstdio>
#include<cstring>
#define LL long long
#define maxn 100008
using namespace std;int n,s,sumedge;
int head[maxn],w[maxn];
long long ans;struct Edge{int x,y,nxt;Edge(int x=0,int y=0,int nxt=0):x(x),y(y),nxt(nxt){}
}edge[maxn];void add(int x,int y){edge[++sumedge]=Edge(x,y,head[x]);head[x]=sumedge;
}LL dfs(int x,int sum){if(sum>s)return 0;if(sum==s)return 1;long long js=0;for(int i=head[x];i;i=edge[i].nxt){int v=edge[i].y;js+=dfs(v,sum+w[v]);}return js;
}int main(){scanf("%d%d",&n,&s);for(int i=1;i<=n;i++)scanf("%d",&w[i]);for(int i=1;i<n;i++){int x,y;scanf("%d%d",&x,&y);add(x,y);}for(int i=1;i<=n;i++)if(w[i]==s)ans++;else ans+=dfs(i,w[i]);cout<<ans<<endl;return 0;
}

#include<iostream>
#include<cstdio>
#include<cstring>
#define maxn 100008
#define LL long long
using namespace std;int n,s,sumedge,cnt,js;
int head[maxn],w[maxn],dad[maxn],fa[maxn],sum[maxn];
LL ans;struct Edge{int x,y,nxt;Edge(int x=0,int y=0,int nxt=0):x(x),y(y),nxt(nxt){}
}edge[maxn];void add(int x,int y){edge[++sumedge]=Edge(x,y,head[x]);head[x]=sumedge;
}void dfs(int x){dad[++js]=x;for(int i=head[x];i;i=edge[i].nxt){int v=edge[i].y;sum[v]=sum[x]+w[v];for(int j=js;j>=0;j--){//要循环到0，可能它自己的点权就是s if(sum[v]-sum[dad[j]]==s)ans++;if(sum[v]-sum[dad[j]]>s)break;}dfs(v);}js--;
}int main(){scanf("%d%d",&n,&s);for(int i=1;i<=n;i++)scanf("%d",&w[i]);for(int i=1;i<n;i++){int x,y;scanf("%d%d",&x,&y);fa[y]=x;add(x,y);}sum[1]=w[1]; dfs(1);cout<<ans<<endl;return 0;
}