#include <algorithm>

#include <cstdio>

#define maxn 310

#define maxm (maxn * maxn / 2 + maxn * 2)

const int inf = 0x3f3f3f3f;

namespace Network_Flow {

	int head[maxn], lst[maxn], cnt = 1;

	struct Edge {

		int to, nxt, w;

	} e[maxm << 1];

	inline void addedge(int a, int b, int c = 1, int d = 0) {

		e[++cnt] = (Edge) { b, head[a], c }; head[a] = cnt;

		e[++cnt] = (Edge) { a, head[b], d }; head[b] = cnt;

	}

	int st, ed, n, MF;

	int GAP[maxn], d[maxn];

	int q[maxn], h, t;

	void init() {

		GAP[d[q[h = t = 0] = ed] = 1] = 1;

		for (int i = st; i <= ed; ++i) lst[i] = head[i];

		while (h <= t) {

			int u = q[h++];

			for (int i = head[u], v; i; i = e[i].nxt) {

				v = e[i].to;

				if (!d[v]) {

					++GAP[d[v] = d[u] + 1];

					q[++t] = v;

				}

			}

		}

	}

	int dfs(int u, int low) {

		if (!low || u == ed) return low;

		int w, res = 0;

		for (int &i = lst[u], v; i; i = e[i].nxt) {

			v = e[i].to;

			if (d[u] == d[v] + 1) {

				w = dfs(v, std::min(low, e[i].w));

				res += w, low -= w;

				e[i].w -= w, e[i ^ 1].w += w;

				if (!low) return res;

			}

		}

		if (!--GAP[d[u]]) d[st] = n + 1;

		++GAP[++d[u]], lst[u] = head[u];

		return res;

	}

	void ISAP(int S, int T) {

		st = S, ed = T, n = T - S + 1;

		init();

		while (d[st] <= n) MF += dfs(st, inf);

	}

}

using Network_Flow::addedge;

int n, m;

int main() {

	scanf("%d%d", &n, &m);

	int st = 0, ed = n + 1;

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

		scanf("%d", &x);

		if (x) addedge(st, i);

		else addedge(i, ed);

	}

	for (int i = 0, a, b; i < m; ++i) {

		scanf("%d%d", &a, &b);

		addedge(a, b, 1, 1);

	}

	Network_Flow::ISAP(st, ed);

	printf("%d\n", Network_Flow::MF);

	return 0;

}