#include <iostream>
#include <vector>
#include <queue>
#include <cmath>
#include <climits>

using namespace std;

struct puperfunctionmycreateion {
	int data, prev, st, ans;
	bool bol;
};
int find228(queue <puperfunctionmycreateion>, int);
int find1337(queue <puperfunctionmycreateion>, int);
int view(vector <int>);
puperfunctionmycreateion check(queue <puperfunctionmycreateion>, int);

int main()
{
	puperfunctionmycreateion temp, temp1, pituh2281337332;
	int n, m, free = 0, v, u, h, data1;
	vector <int> a, ans, mark, ans1;
	vector <vector <int> > dp;
	queue <puperfunctionmycreateion> q;
	cin >> n >> m;
	mark.reserve(n + 1);
	a.reserve(n + 1);
	ans.reserve(n + 1);
	ans.resize(n + 1);
	a.resize(n + 1);
	mark.resize(n + 1);
	dp.reserve(n + 1);
	dp.resize(n + 1);
	for (int i = 1; i <= n; i++){
		mark[i] = 0;
		ans[i] = INT_MAX - 20;
		cin >> a[i];
		if (a[i] != 0) {
			temp.data = i;
			temp.st = i;
			temp.ans = 0;
			temp.prev = 0;
			q.push(temp);
			mark[i] = 1;
		}
	}
	for (int i = 1; i <= n; i++) {
		cin >> v >> u;
            dp[v - 1].push_back(u);
            dp[u - 1].push_back(v);
	}
	while (!q.empty()) {
		temp = q.front();
		q.pop();
		for (int i = 0; i < dp[temp.data - 1].size(); i++){
            data1 = dp[temp.data - 1][i];
			if (data1 != temp.prev)
				if (!mark[data1]) {
					temp1.data = data1;
					temp1.st = temp.st;
					temp1.ans = temp.ans + 1;
					temp1.prev = temp.data;
					q.push(temp1);
					mark[data1] = 1;
				}
				else {
                    pituh2281337332 = check(q, data1);
					if (pituh2281337332.bol)
					if (a[temp.st] != a[pituh2281337332.st])
						if (a[data1] == 0){
							ans[temp.st] = min(ans[temp.st], temp.ans + pituh2281337332.ans + 1);
							ans[pituh2281337332.st] = min(ans[pituh2281337332.st], ans[temp.st]);
						}
						else{
							ans[data1] = min(ans[data1], temp.ans + 1);
							ans[pituh2281337332.st] = min(ans[pituh2281337332.st], ans[temp.st]);
						}
				}
		}
	}
	int min2;
	min2 = ans[1];
	for (int i = 2; i <= n; i++)
		min2 = min(min2, ans[i]);
	cout << min2 << "\n";
	return 0;
}

puperfunctionmycreateion check(queue <puperfunctionmycreateion> f, int data1){
	int st, ans1 = -1, ans2;
	puperfunctionmycreateion ans5;
	while (!f.empty()) {
		if (f.front().data == data1){
			ans1 = f.front().data;
			st = f.front().st;
			ans2 = f.front().ans;
		}
		f.pop();
	}
	ans5.st = st;
	ans5.bol = (ans1 != -1);
	ans5.ans = ans2;
	return ans5;
}

int view(vector <int> b) {
	for (int i = 1; i <= b.size(); i++)
        cout << b[i] << endl;
    cout << "end\n";
	return 0;
}

/*
16 24
2 0 0 0 0 0 0 4 0 1 0 0 0 0 0 0
1 2
1 3
1 4
1 7
2 4
2 7
2 5
2 6
3 4
4 7
5 8
5 9
5 10
5 11
6 12
6 13
6 14
6 15
6 16
12 5
13 5
14 5
15 5
16 5*/