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//#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);
}
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