//#include <gtest/gtest.h>

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

using std::vector;
//using std::pair;

void explore(vector<vector<int>> &adj, int v, vector<int> &visited, vector<int> &prev,
		vector<int> &postv, vector<int> &clock) {
	visited.push_back(v);
	prev[v] = clock[0];
	clock[0] = clock[0] + 1;

	for (size_t i = 0; i < adj[v].size(); i++) {
		if (std::find(visited.begin(), visited.end(), adj[v][i])
				== visited.end())
			explore(adj, adj[v][i], visited, prev, postv, clock);
	}
	postv[v] = clock[0];
	clock[0] = clock[0] + 1;

}

void dfs(vector<vector<int>> &adj, vector<int> &visited, vector<int> &prev,
		vector<int> &postv, vector<int> &clock) {
	for (size_t v = 0; v < adj.size(); v++) {
		if (std::find(visited.begin(), visited.end(), v) == visited.end())
			explore(adj, v, visited, prev, postv, clock);
	}
}

int acyclic(vector<vector<int> > &adj) {
	vector<int> visited;
	vector<int> prev(adj.size(), 0);
	vector<int> postv(adj.size(), 0);
	vector<int> clock(1, 0);
	dfs(adj, visited, prev, postv, clock);

	for (size_t u = 0; u < adj.size(); u++) {
		for (size_t i = 0; i < adj[u].size(); i++) {
			if (postv[u] <= postv[adj[u][i]])
				return 1;
		}
	}
	return 0;
}

//TEST(Acyclicity, ac1) {
//	vector<vector<int>> adj = { { 1 }, { 2 }, { 0 }, { 0 } };
//	ASSERT_EQ(acyclic(adj), 1);
//}

int main() {
  size_t n, m;
  std::cin >> n >> m;
  vector<vector<int> > adj(n, vector<int>());
  for (size_t i = 0; i < m; i++) {
    int x, y;
    std::cin >> x >> y;
    adj[x - 1].push_back(y - 1);
  }
  std::cout << acyclic(adj);
}