#include<bits/stdc++.h>
using namespace std;
#define light ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define dd double
#define int long long
#define pb push_back

#define vv(t) vector<vector<t> >
#define um(a, b) unordered_map<a, b>
#define om(a, b) map<a, b>

#define loop(var, a, b) for(var=0;var<b;var++)

#define INF 1e9
#define mod 998244353

const int nax = 555, inf = 1e18;
struct node
{
    int n1, n2;
    vector<set<int>> g;
    vector<int> tl, tr;
    node() {}
    node(int n1, int n2): n1(n1), n2(n2) {
        g.resize(n1);
    }
    void init()
    {
        tl = vector<int>(n2, -1);
    }
    int find(int x)
    {
        if (tr[x] == 1)
            return 0;
        tr[x] = 1;
        for (auto it : g[x])
            if (tl[it] == -1 or find(tl[it]) == 1)
            {
                tl[it] = x;
                return 1;
            }
        return 0;
    }
    int val()
    {
        init();
        int res = 0;
        for (int i = 0; i < n1; i++)
        {
            tr = vector<int>(n1, 0);
            res += find(i);
        }
        return res;
    }
    void rem(int v, int r)
    {
        if (r)
        {
            for (int i = 0; i < n1; i++)
                g[i].erase(v);
        }
        else
            g[v].clear();
    }
    void add(int x, int y)
    {
        g[x].insert(y);
    }
};
int n, m, k, dp[nax][nax], p[nax][nax], x[nax], y[nax];
vector<int> g[nax];

int32_t main()
{
    cin >> n >> m >> k;
    for (int i = 0; i < m; i++)
    {
        int u, v;
        cin >> u >> v;
        --u;
        --v;
        g[u].push_back(v);
    }
    for (int i = 0; i < k; i++)
        cin >> x[i] >> y[i];
    node root(n, n);
    for (int i = 0; i < n; i++)
        for (auto j : g[i])
            root.add(i, j);
    int cnt = root.val(), cur = cnt;
    vector<int> st, res;
    while (cur > 0)
    {
        int ptr = 0;
        for (int i = 0; i < n; i++)
        {
            node rr = root;
            rr.rem(i, 0);
            if (rr.val() < cur)
                ptr = i + 1;
            rr = root;
            rr.rem(i, 1);
            if (rr.val() < cur)
                ptr = -(i + 1);
        }
        st.push_back(ptr);
        root.rem(abs(ptr) - 1, ptr < 0);
        cur--;
    }
    reverse(st.begin(), st.end());
    for (int i = 0; i <= k; i++)
        for (int j = 0; j <= cnt; j++)
            dp[i][j] = -inf;
    dp[0][cnt] = 0;
    for (int i = 0; i < k; i++)
        for (int j = 0; j <= cnt; j++)
        {
            if (dp[i][j] == -inf)
                continue;
            for (int z = 0; z <= j; z++)
            {
                if (i + z + 1 >= n)
                    continue;
                int pp = j - z;
                int ad = max(0LL, x[i] - pp * y[i]);
                if (dp[i + 1][z] < dp[i][j] + ad)
                {
                    dp[i + 1][z] = dp[i][j] + ad;
                    p[i + 1][z] = j;
                }
            }
        }
    cur = max_element(dp[k], dp[k] + cnt + 1) - dp[k];
    for (int i = k; i > 0; i--)
    {
        res.push_back(0);
        for (int j = p[i][cur] - 1; j >= cur; j--)
            res.push_back(st[j]);
        cur = p[i][cur];
    }
    reverse(res.begin(), res.end());
    cout << res.size() << '\n';
    for (auto x : res)
        cout << x << ' ';
    return 0;
}
