#include<bits/stdc++.h>
using namespace std;
const int N=5100;
vector<int>G[N];
int tsp,cnt,scc[N],low[N],dfn[N];
stack<int>stk;bool instk[N];

void tarjan(int x)
{
    low[x]=dfn[x]=++tsp;
    stk.push(x);instk[x]=true;
    for(int y:G[x])
    {
        if(dfn[y]==0)
        {
            tarjan(y);
            low[x]=min(low[x],low[y]);
        }
        else if(instk[y]==true)low[x]=min(low[x],dfn[y]);

    }
    if(low[x]==dfn[x])
    {
        cnt++;
        for(int z=-1;z!=x;)
        {
           z=stk.top();stk.pop();instk[z]=false;
           scc[z]=cnt;
        }
    }
}

int main()
{
    int n,m;
    while(scanf("%d", &n)!=EOF&&n)
    {
        scanf("%d", &m);
        memset(G,0,sizeof(G));
        for(int i=1,x,y;i<=m;i++) {
            scanf("%d%d", &x, &y);
            G[x].push_back(y);
        }
    
        tsp=cnt=0;memset(low,0,sizeof(low));memset(dfn,0,sizeof(dfn));
        memset(scc,0,sizeof(scc));memset(instk,0,sizeof(instk));
        for(int i=1;i<=n;i++)if(dfn[i]==0)tarjan(i);
 
        vector<int>cd(cnt+1);
        for(int i=1;i<=n;i++)for(int j:G[i])if(scc[i]!=scc[j])cd[scc[i]]++;
        for(int i=1;i<=n;i++)if(cd[scc[i]]==0)printf("%d ", i);
        printf("\n");
    }
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int N=5100;
vector<int>G[N];
int tsp,cnt,scc[N],low[N],dfn[N];
stack<int>stk;bool instk[N];

void tarjan(int x)
{
    low[x]=dfn[x]=++tsp;
    stk.push(x);instk[x]=True;
    for(int y:G[x])
    {
        if(dfn[y]==0)
        {
            tarjan(y);
            low[x]=min(low[x],low[y]);
        }
        else if(instk[y]==True)low[x]=min(low[x],dfn[y]);

    }
    if(low[x]==dfn[x])
    {
        cnt++;
        for(int z=-1;z!=x;)
        {
           z=stk.top();stk.pop();instk[z]=False;
           scc[z]=cnt;
        }
    }
}

int main()
{
    int n,m;
    while(scanf("%d",&n)!=EOF&&n)
    {
        scanf("%d",&m);
        memset(G,0,sizeof(G));
        for(int i=1,x,y;i<=m;i++)scanf("%d%d",&x,&y),G[x].push_back(y);
    
        tsp=cnt=0;memset(low,0,sizeof(low));memset(dfn,0,sizeof(dfn));
        memset(scc,0,sizeof(scc));memset(instk,0,sizeof(instk));
        for(int i=1;i<=n;i++)if(dfn[i]==0)tarjan(i);
 
        vector<int>cd(cnt+1);//所在连通分支没有出度的点为sink点 
        for(int i=1;i<=n;i++)for(int j:G[i])if(scc[i]!=scc[j])cd[scc[i]]++;
        for(int i=1;i<=n;i++)if(cd[scc[i]]==0)printf("%d ",i);
        printf("\n");
    }
    return 0;
}