P

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

int a[200][200];
int d[200][200];
pair<int, int> p[200][200];
const int INF = 1000000000;
int main()
{
    int n, m, g, t;
    cin >> m >> n >> g >> t;
    for (int i = 0; i <= m; i++) {
        for (int j = 0; j <= n; j++) {
            a[i][j] = 0;
            d[i][j] = -INF;
        }
    }
    d[1][1] = 0;
    p[1][1] = { -1, -1 };
    for (int i = 0; i < g; i++) {
        int q, w;
        cin >> q >> w;
        a[q][w] = 1;
    }
    for (int i = 0; i < t; i++) {
        int q, w;
        cin >> q >> w;
        a[q][w] = -1;
    }
    for (int i = 1; i <= m; i++) {
        for (int j = 1; j <= n; j++) {
            if (a[i][j] == -1) {
                continue;
            }
            if (d[i - 1][j] >= 0) {
                d[i][j] = d[i - 1][j];
                p[i][j] = { i - 1, j };
            }
            if (d[i][j - 1] >= 0 && d[i][j - 1] > d[i][j]) {
                d[i][j] = d[i][j - 1];
                p[i][j] = { i, j - 1 };
            }
            if (a[i][j] == 1) {
                d[i][j]++;
            }
        }
    }

    if (d[m][n] >= 0) {
        cout << d[m][n] << endl;
        pair<int, int> r = { m, n };
        vector<pair<int, int> > ans;
        ans.push_back({ m, n });
        while (p[r.first][r.second].first != -1) {
            ans.push_back(p[r.first][r.second]);
            r = p[r.first][r.second];
        }
        for (int i = ans.size() - 1; i >= 0; i--) {
            cout << ans[i].first << ' ' << ans[i].second << endl;
        }
    }
    else {
        cout << -1;
    }
}