#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <stack>using namespace std;#define mnx 5020#define mxe 2500020int fst[mnx], nxt[mxe], to[mxe], e;void init() {memset(fst, -1, sizeof fst);e = 0;}void add(int u, int v) {to[e] = v, nxt[e] = fst[u], fst[u] = e ++;}int pre[mnx], sccno[mnx], dc, scnt;int n, m;stack<int> S;int dfs(int u) {int lowu = pre[u] = ++dc;S.push(u);for(int i = fst[u]; ~i; i = nxt[i]) {int v = to[i];if(!pre[v]) {int lowv = dfs(v);lowu = min(lowu, lowv);}else if(!sccno[v])lowu = min(lowu, pre[v]);}if(lowu == pre[u]) {++scnt;while(1) {int x = S.top(); S.pop();sccno[x] = scnt;if(x == u) break;}}return lowu;}bool out[mnx];int ans[mnx], len;int main() {while(scanf("%d", &n) && n) {scanf("%d", &m);init();while(m--) {int u, v;scanf("%d%d", &u, &v);add(u, v);}memset(pre, 0, sizeof pre);memset(sccno, 0, sizeof sccno);dc = scnt = 0;for(int i = 1; i <= n; ++i)if(!pre[i])dfs(i);memset(out, 0, sizeof out);for(int i = 1; i <= n; ++i)for(int j = fst[i]; ~j; j = nxt[j]) {int v = to[j];if(sccno[v] != sccno[i])out[sccno[i]] = 1;}len = 0;for(int i = 1; i <= n; ++i)if(out[sccno[i]] == 0)ans[len++] = i;for(int i = 0; i < len; ++i)printf("%d%c", ans[i], i == len - 1? 'n': ' ');}return 0;}
