#include <bits/stdc++.h>

using namespace std;

int dp[100100][4], mark[100100];

vector <int> adj[100100], child[100100];

void dfs(int u){

mark[u] = 1;

for(int i = 0; i < adj[u].size(); ++i){

if(!mark[adj[u][i]]){

child[u].push_back(adj[u][i]);

dfs(adj[u][i]);

}

}

}

/*int vc(int u, int use){

if(dp[u][use] != -1) return dp[u][use];

if(child[u].size() == 0) return use;

dp[u][use] = use;

if(use)

for(int i = 0; i < child[u].size(); ++i)

dp[u][use] += min(vc(child[u][i], 0), vc(child[u][i], 1));

else for(int i = 0; i < child[u].size(); ++i)

dp[u][use] += vc(child[u][i], 1);

return dp[u][use];

}*/

int vc(int u, int ft_use){

if(dp[u][ft_use] != -1) return dp[u][ft_use];

if(child[u].size() == 0) return 1 - (ft_use > 1);

int used = 1, not_used = 0;

for(int i = 0; i < child[u].size(); ++i)

used += vc(child[u][i], 2);

if(ft_use == 0)

return used;

else if(ft_use == 1){

}

for(int i = 0; i < child[u].size(); ++i)

used += vc(child[u][i], 1);

else

}

int main(){

cin.tie(0);

ios_base::sync_with_stdio(0);

int n, tr, a, b;

cin >> n;

for(int i = 0; i < n; ++i) cin >> tr >> tr;

for(int i = 1; i < n; ++i){

cin >> a >> b;

adj[a].push_back(b);

adj[b].push_back(a);

}

for(int i = 0; i <= n ; ++i)

for(int j = 0; j < 4; ++j)

dp[i][j] = -1;

dfs(1);

cout << n - min(vc(1, 0), vc(1, 1)) << "\n";

return 0;

}