import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

/**
 * 
5
3
1 3
2 3
2 4


5
8
1 4
1 2
2 4
2 3
4 3
4 5
3 5
4 1

5
8
1 4
1 2
2 4
2 3
4 3
4 5
3 5
4 2

5
7
1 4
1 2
2 4
2 3
4 3
4 5
3 5


 */
public class TopologicalSort {

	static int maxn; // 頂點數
	static
 
 int edgen; // 邊數
	static int[][] graph; // 圖
	static int[] indegree;  // 每個點的入度
	static int[] vstd;  // 點的訪問狀態
	static List<Integer> topo = new ArrayList<Integer>(); //結果

	static boolean cyclic = false;
	static void dfs(int u) {
		if(cyclic) {
			return;
		}
		vstd[u] = -1;  // 正在搜尋中
		for (int i =
 
 1; i < maxn && !cyclic; i++) {
			if (graph[u][i] == 1) {
				if(vstd[i] == -1) { // 正在搜尋中的點被再次搜尋，說明存在環
					System.out.println("存在有向環");
					cyclic = true;
					return;
				} else if(vstd[i] == 0) {
					dfs(i);					
				}
			}
		}
		topo.add(u);
		vstd[u] = 1;
	}

	public static void main
 
(String[] args) {
		Scanner scan = new Scanner(System.in);
		maxn = scan.nextInt() + 1; //
		edgen = scan.nextInt();
		graph = new int[maxn][maxn];
		indegree = new int[maxn];
		vstd = new int[maxn];
		
		for (int i = 0; i < edgen; i++) {
			int u = scan.nextInt();
			int v = scan.nextInt();
			graph[u][v] = 1;
			indegree[v]++;
		}
		scan.close();
		List<Integer> zeroDegree = new ArrayList<Integer>();
		for (int u = 1; u < maxn; u++) {
			for (int v = 1; v < maxn; v++) {
				// 從入度為0的頂點開始搜尋
				if (indegree[u] == 0 && graph[u][v] == 1) {
					zeroDegree.add(u);
					break;
				}
			}
		}
		
		if(zeroDegree.size() == 0) {
			System.out.println("不存在入度為0的頂點，即存在閉環");
			return;
		}
		
		for(int u : zeroDegree) {
			dfs(u);
		}
		if(cyclic) {
			return;
		}
		Collections.reverse(topo);
		for (int n : topo) {
			System.out.print(n);
		}
	}

}