import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;
import java.util.StringTokenizer;

import acm.program.ConsoleProgram;

public class TopologicalSorting extends ConsoleProgram {

    public void run() {
        HashMap<Integer, ArrayList<Integer>> map = new HashMap<Integer, ArrayList<Integer>>();

        String s = readLine("Enter n of subjects and n of limitations: ");
        int subject = 0, limit = 0;
        StringTokenizer tk = new StringTokenizer(s);
        subject = Integer.valueOf(tk.nextToken());
        limit = Integer.valueOf(tk.nextToken());
        for (int i = 0; i < limit; i++) {
            int pre = 0, sub = 0;
            String lim = readLine();
            StringTokenizer tok = new StringTokenizer(lim);
            pre = Integer.valueOf(tok.nextToken());
            sub = Integer.valueOf(tok.nextToken());
            if (map.containsKey(sub)) {
                ArrayList<Integer> array = map.get(sub);
                array.add(pre);
                map.put(sub, array);
            } else {
                ArrayList<Integer> array = new ArrayList<Integer>();
                array.add(pre);
                map.put(sub, array);
            }
        }

        Set<Integer> set = new HashSet<Integer>();
        String sequence = readLine("Enter sequence: ");
        StringTokenizer tok = new StringTokenizer(sequence);
        set.add(Integer.valueOf(tok.nextToken()));
        while (tok.hasMoreTokens()) {
            int i = Integer.valueOf(tok.nextToken());
            if (!map.containsKey(i)) continue;
            for (int j = 0; j < map.get(i).size(); j++) {
                if (!set.contains(map.get(i).get(j))) {
                    println("false");
                    return;
                }
            }
            set.add(i);
        }
        println("true");
    }
}