#include<bits/stdc++.h>
using namespace std;

int const MAXN=501;

vector<vector<int> > graph(MAXN);
int degree[MAXN]={0};

vector<int> Topo(int n){
    priority_queue<int,vector<int> ,greater<int> > node;
    vector<int> ans;
    for(int i=1;i<=n;i++){
        if(degree[i]==0){
            node.push(i);
        }
    }
    while(!node.empty()){
        int u=node.top();
        node.pop();
        ans.push_back(u);
        for(int i=0;i<graph[u].size();i++){
            int v=graph[u][i];
            degree[v]--;
            if(degree[v]==0){
                node.push(v);
            }
        }
    }
    return ans;
}

int main(){
    int n,m;
    while(cin>>n>>m){
        if(n==0&&m==0){
            break;
        }
        while(m--){
            int win,lose;
            cin>>win>>lose;
            graph[win].push_back(lose);
            degree[lose]+...