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import java.util.ArrayList;
import java.util.Scanner;
public class Acyclicity {
static int acyclic(ArrayList<ArrayList<Integer>> adj) {
ArrayList<Integer> visited = new ArrayList<>();
int[] prev = new int[adj.size()];
int[] postv = new int[adj.size()];
int[] clock = new int[1];
clock[0] = 0;
dfs(adj, visited, prev, postv, clock);
for (int u = 0; u < adj.size(); u++) {
for (int v : adj.get(u)) {
if (postv[u] <= postv[v])
return 1;
}
}
return 0;
}
private static void dfs(ArrayList<ArrayList<Integer>> adj, ArrayList<Integer> visited, int[] prev, int[] postv, int[] clock) {
for (int v = 0; v < adj.size(); v++) {
if (!visited.contains(v))
explore(adj, v, visited, prev, postv, clock);
}
}
private static void explore(ArrayList<ArrayList<Integer>> adj, int v, ArrayList<Integer> visited, int[] prev, int[] postv, int[] clock) {
visited.add(v);
prev[v] = clock[0];
clock[0] = clock[0] + 1;
for (int n : adj.get(v)) {
if (!visited.contains(n))
explore(adj, n, visited, prev, postv, clock);
}
postv[v] = clock[0];
clock[0] = clock[0] + 1;
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
int m = scanner.nextInt();
ArrayList<ArrayList<Integer>> adj = new ArrayList<ArrayList<Integer>>();
for (int i = 0; i < n; i++) {
adj.add(new ArrayList<Integer>());
}
for (int i = 0; i < m; i++) {
int x, y;
x = scanner.nextInt();
y = scanner.nextInt();
adj.get(x - 1).add(y - 1);
}
System.out.println(acyclic(adj));
}
}
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