#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <bitset>
#define Buff ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
using namespace std;
typedef long long ll;
const int inf = 0x3f3f3f3f;
const int N = 705;

struct LB
{
	int to, nx;
}b[700 * 710];
int hd[710], idx;
void ini()
{
	idx = 1;
	for(int i = 0; i < 710; i++)
		hd[i] = -1;
}
void add(int x, int y)
{
	b[idx].to = y;
	b[idx].nx = hd[x];
	hd[x] = idx++;
}

int dx;
vector<int> vis[710];

bool vvis[710];
void dfs(int u)
{
	if(vvis[u])
		return;
	vvis[u] = 1;
	vis[u].emplace_back(dx);
	for(int i = hd[u]; i != -1; i = b[i].nx)
	{
		dfs(b[i].to);
	}
}

int c[N], w[N];
int sum[710][710];

void solve()
{
	ini();
	int n, m;
	cin >> n >> m;
	for(int i = 1; i <= n; i++) cin >> c[i];
	for(int i = 1; i <= n; i++) cin >> w[i];

	for(int i = 1; i <= m; i++)
	{
		int u, v;
		cin >> u >> v;
		add(u, v);
	}

	for(int i = 1; i <= n; i++)
	{
		if(c[i] == 1)
		{
			dx = i;
			memset(vvis, 0, sizeof(vvis));
			dfs(i);
		}
	}

	vector<int> c1, c2;
	for(int i = 1; i <= n; i++)
	{
		if(c[i] != 1)
		{
			c2.emplace_back(i);
			if(vis[i].empty())
				continue;
			for(auto& j : vis[i])
			{
				sum[j][c[i]] += w[i];
			}
		}
		else
			c1.emplace_back(i);
	}

	double mx = -1;
	for(auto& i : c2)
	{
		ll a1 = 0, a2 = 0;
		for(auto& j : c1)
		{
			if(sum[j][c[i]] >= w[j])
			{
				ll fz = sum[j][c[i]];
				ll fm = w[j];
				if(a2 == 0 || fz * 1.0 / fm > a1 * 1.0 / a2)
				{
					a1 = fz;
					a2 = fm;
				}
			}
		}
		if(a2 > 0)
			mx = max(mx, a1 * 1.0 / a2);
	}
	cout << (ll)mx << '\n';
}

int main()
{
	Buff;
	int N = 1;
	//cin >> N;
	while(N--)
		solve();
	return 0;
}