#include <iostream>
#include <vector>

using namespace std;

const int maxn = 52013;

struct Edge{
	int to;
};

vector<Edge*> edges[maxn];
int n,d,ans;

void Add(int u,int v){
	Edge* e = new Edge;
	e->to = v;
	edges[u].push_back(e);
}

void DFS(int now,int fa,int deep){
	if(deep <= d) ans++;
	for(Edge* p : edges[now]){
		if(p->to != fa){
			DFS(p->to,now,deep+1);
		}
	}
}

int main(){
	cin>>n>>d;
	for(int i = 1;i <= n-1;i++){
		int u,v;
		cin>>u>>v;
		Add(u,v);Add(v,u);
	}
	DFS(1,0,0);
	cout<<ans-1<<endl;
	return 0;
}

这段代码在本地和在线IDE都能跑，提交就RE，搞不懂。