#include <iostream>
#include <map>
#include <list>

using namespace std;

map<int, list<int> > adj;
int n, m;
map<int, bool> visited;

void dfs(int i) {
  cout << i<<endl;
  visited[i] = true;
  for (list<int>::iterator j = adj[i].begin(); j!=adj[i].end(); j++) {
    if (! visited[*j]) 
      dfs(*j);    
  }
}

int main() {

  cin >> n >> m;
  for (int i=0; i<m; i++) {
    int x, y;
    cin >> x >> y;
    adj[x].push_back(y);
  }

  for(int x=0; x<n; x++) 
    if (! visited[x]) 
      dfs(x);      
  
  return 0;
}