#include<cstdio>
#include<cstring>
#include<vector>
#include<stack>
using namespace std;
#define N 100010
int n,m,sd,pd,id[N],low[N],dfn[N];
bool mark[N];
stack<int>s;
vector<int>grap[N];
void tarjan(int v){
    low[v]=dfn[v]=++pd;
    mark[v]=1;
    s.push(v);
    for(int i=0;i<grap[v].size();i++){
        int w=grap[v][i];
        if(!dfn[w]){
            tarjan(w);
            low[v]=min(low[v],low[w]);
        }
        else if(mark[w]){
            low[v]=min(low[v],dfn[w]);
        }
    }
    int u;
    if(low[v]==dfn[v]){
        sd++;
        do{
            u=s.top();
            s.pop();
            id[u]=sd;
            mark[u]=0;
        }while(u!=v);
    }
}
int main(){
    freopen("buss.in","r",stdin);
    freopen("buss.out","w",stdout);
    while(scanf("%d",&n)==1){
        if(!n) break;
        scanf("%d",&m);
        if(n==1&&m==0){printf("1");continue;}
        sd=0;pd=0;
        memset(low,0,sizeof low);
        memset(dfn,0,sizeof dfn);
        memset(mark,0,sizeof mark);
        memset(id,0,sizeof id);
        while(!s.empty()) s.pop();
        for(int i=1,x,y;i<=m;i++) scanf("%d%d",&x,&y),grap[x].push_back(y);
        for(int i=1;i<=n;i++) if(!dfn[i]) tarjan(i);
        int in[N]={0},out[N]={0};
        for(int i=1;i<=n;i++){
            for(int j=0;j<grap[i].size();j++){
                int k=grap[i][j];
                if(id[i]!=id[k]){
                    in[id[k]]++;
                    out[id[i]]++;
                }
            }
        }
        for(int i=1;i<=n;i++) if(!out[id[i]]) printf("%d ",i);putchar(‘\n‘);
        for(int i=1;i<=n;i++) grap[i].clear();
    }
    return 0;
}