#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
#define pb push_back
#define mp make_pair

#define MAXN 10000


struct Dinic {
	struct Edge {
		int to, rev;
		ll c, oc;
		ll flow() { return max(oc - c, 0LL); } // if you need flows
	};
	vi lvl, ptr, q;
	vector<vector<Edge>> adj;
	Dinic(int n) : lvl(n), ptr(n), q(n), adj(n) {}
	void addEdge(int a, int b, ll c, ll rcap = 0) {
		adj[a].push_back({b, sz(adj[b]), c, c});
		adj[b].push_back({a, sz(adj[a]) - 1, rcap, rcap});
	}
	ll dfs(int v, int t, ll f) {
		if (v == t || !f) return f;
		for (int& i = ptr[v]; i < sz(adj[v]); i++) {
			Edge& e = adj[v][i];
			if (lvl[e.to] == lvl[v] + 1)
				if (ll p = dfs(e.to, t, min(f, e.c))) {
					e.c -= p, adj[e.to][e.rev].c += p;
					return p;
				}
		}
		return 0;
	}
	ll calc(int s, int t) {
		ll flow = 0; q[0] = s;
		rep(L,0,31) do { // 'int L=30' maybe faster for random data
			lvl = ptr = vi(sz(q));
			int qi = 0, qe = lvl[s] = 1;
			while (qi < qe && !lvl[t]) {
				int v = q[qi++];
				for (Edge e : adj[v])
					if (!lvl[e.to] && e.c >> (30 - L))
						q[qe++] = e.to, lvl[e.to] = lvl[v] + 1;
			}
			while (ll p = dfs(s, t, LLONG_MAX)) flow += p;
		} while (lvl[t]);
		return flow;
	}
	bool leftOfMinCut(int a) { return lvl[a] != 0; }
};

vi adj[MAXN];

int main() {
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);

	int n, m;
	cin >> n >> m;
	rep(i, 0, m) {
		int u, v;
		cin >> u >> v;
		u--; v--;
		adj[u].pb(v);
		adj[v].pb(u);
	}

	string s;
	cin >> s;

	Dinic flow(2*n + 2);
	const int a = 2*n;
	const int b = a + 1;

	rep(i, 0, n) {
		int v0, v1;
		if (s[i] == '0') {
			v0 = i;
			v1 = n + i;
			flow.addEdge(a, v0, 2);
			flow.addEdge(v1, b, 1);
			flow.addEdge(v0, v1, 1e8);
		} else {
			v0 = n + i;
			v1 = i;
			flow.addEdge(a, v1, 1);
			flow.addEdge(v0, b, 2);
			flow.addEdge(v1, v0, 1e8);
		}
		for (int x : adj[i]) {
			int vx0, vx1;
			if (s[x] == '0') {
				vx0 = x;
				vx1 = n + x;
				// can't both be 0, can't both be 1
				flow.addEdge(vx0, v0, 1e8);
				flow.addEdge(v1, vx1, 1e8);
			} else {
				vx0 = n + x;
				vx1 = x;
				// can't both be 0, can't both be 1
				flow.addEdge(v0, vx0, 1e8);
				flow.addEdge(vx1, v1, 1e8);
			}
		}
	}

	int mvc = flow.calc(a, b);
	int mis = 3*n - mvc;
	int out = 2*n - mis;
	cout << out << endl;
}