KOM

#include <iostream>

using namespace std;

typedef struct Node {
    int n;
    struct Node* next;
} Node;

enum color {
    white,
    gray,
    black
};

bool find_cycle_from(Node** graph, color* visited, int n, int x) {
    // gray color means "we already processed this node in current lookup" - once x is gray, we are sure we've got a cycle
    visited[x] = gray;
    Node* neighbor = graph[x];
    while(neighbor != NULL) {
        if(visited[neighbor->n] == gray) return true;
        if(visited[neighbor->n] == white && find_cycle_from(graph, visited, n, neighbor->n)) return true;
        neighbor = neighbor->next;
    }

    visited[x] = black;
    return false;
}

bool has_cycle(Node** graph, int n) {
    color visited[n];
    for (int i=0; i<n; i++) visited[i] = white;
    for(int i = 0; i<n; i++) {
        if (visited[i] == white) {
            if (find_cycle_from(graph, visited, n, i)) return true;
        }
    }
    return false;
}

int main() {
    int n, k;
    cin >> n;
    Node **graph = new Node*[n];
    for(int i=0;i<n;i++) graph[i] = NULL;
    cin >> k;
    for(int i=0; i<k; i++) {
        Node* tmp = new Node;
        int x, y;
        cin >> x;
        cin >> y;
        if(x > n) {
            return 44;
        }
        if(y > n) {
            return 45;
        }
        tmp->n = y;
        tmp->next = graph[x];
        graph[x] = tmp;
    }
    cout << (has_cycle(graph, n) ? "CYKL" : "OK") << endl;
}