#include <bitset>
#include <deque>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <algorithm>
#include <functional>
#include <iterator>
#include <locale>
#include <memory>
#include <stdexcept>
#include <utility>
#include <string>
#include <fstream>
#include <ios>
#include <iostream>
#include <iosfwd>
#include <iomanip>
#include <istream>
#include <ostream>
#include <sstream>
#include <streambuf>
#include <complex>
#include <numeric>
#include <valarray>
#include <exception>
#include <limits>
#include <new>
#include <typeinfo>
#include <cassert>
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <climits>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdlib>
#include <cstddef>
#include <cstdarg>
#include <ctime>
#include <cstdio>
#include <cstring>
#include <cwchar>
#include <cwctype>
using namespace std;
static const double EPS = 1e-8;
static const double PI = 4.0 * atan(1.0);
static const double PI2 = 8.0 * atan(1.0);
typedef long long ll;
typedef unsigned long long ull;

#define ALL(c) (c).begin(), (c).end()
#define CLEAR(v) memset(v,0,sizeof(v))
#define MP(a,b) make_pair((a),(b))
#define REP(i,n) for(int i=0;i<(int)n;++i)
#define ABS(a) ((a)>0?(a):-(a))
template<class T> T MIN(const T& a, const T& b) { return a < b ? a : b; }
template<class T> T MAX(const T& a, const T& b) { return a > b ? a : b; }
template<class T> void MIN_UPDATE(T& a, const T& b) { if (a > b) a = b; }
template<class T> void MAX_UPDATE(T& a, const T& b) { if (a < b) a = b; }

typedef int Weight;
struct Edge {
  int src, dst;
  Weight weight;
  Edge(int src, int dst, Weight weight) :
    src(src), dst(dst), weight(weight) { }
};
bool operator < (const Edge &e, const Edge &f) {
  return e.weight != f.weight ? e.weight > f.weight : // !!INVERSE!!
    e.src != f.src ? e.src < f.src : e.dst < f.dst;
}
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

typedef vector<Weight> Array;
typedef vector<Array> Matrix;

static const int INF = INT_MAX / 3;

#define RESIDUE(s,t) (capacity[s][t]-flow[s][t])
Weight augment(const Graph &g, const Matrix &capacity, Matrix &flow,
    const vector<int> &level, vector<bool> &finished, int u, int t, Weight cur) {
  if (u == t || cur == 0) return cur;
  if (finished[u]) return 0;
  finished[u] = true;
  for (Edges::const_iterator e = g[u].begin(), eEnd = g[u].end(); e != eEnd; ++e) if (level[e->dst] > level[u]) {
    Weight f = augment(g, capacity, flow, level, finished,
        e->dst, t, min(cur, RESIDUE(u, e->dst)));
    if (f > 0) {
      flow[u][e->dst] += f; flow[e->dst][u] -= f;
      finished[u] = false;
      return f;
    }
  }
  return 0;
}
Weight maximumFlow(const Graph &g, int s, int t, Matrix& flow, Matrix& capacity) {
  int n = g.size();
  flow.resize(n, Array(n));
  capacity.resize(n, Array(n)); // adj. matrix
  REP(u,n) for (Edges::const_iterator e = g[u].begin(), eEnd = g[u].end(); e != eEnd; ++e) capacity[e->src][e->dst] += e->weight;

  Weight total = 0;
  for (bool cont = true; cont; ) {
    cont = false;
    vector<int> level(n, -1); level[s] = 0; // make layered network
    queue<int> Q; Q.push(s);
    for (int d = n; !Q.empty() && level[Q.front()] < d; ) {
      int u = Q.front(); Q.pop();
      if (u == t) d = level[u];
      for (Edges::const_iterator e = g[u].begin(), eEnd = g[u].end(); e != eEnd; ++e) if (RESIDUE(u,e->dst) > 0 && level[e->dst] == -1)
        Q.push(e->dst), level[e->dst] = level[u] + 1;
    }
    vector<bool> finished(n); // make blocking flows
    for (Weight f = 1; f > 0; ) {
      f = augment(g, capacity, flow, level, finished, s, t, INF);
      if (f == 0) break;
      total += f; cont = true;
    }
  }
  return total;
}
int main() {
	for (int N, M; cin >> N >> M && (N || M);) {
		Graph g(N + 1);
		Edges edges;
		REP(m, M) {
			int s, t;
			cin >> s >> t;
			const Edge edge(s, t, 1);
			g[s].push_back(edge);
			g[t].push_back(Edge(t, s, 1));
			edges.push_back(edge);
		}

		int s, t;
		cin >> s >> t;

		Matrix flow, capacity;
		const Weight w = maximumFlow(g, s, t, flow, capacity);

		cout << w << endl;

		vector<int> reversed;
		REP(m, M) {
			const Edge& edge = edges[m];
			if (flow[edge.dst][edge.src] > 0) {
				reversed.push_back(m + 1);
			}
		}

		cout << reversed.size() << endl;
		REP(i, reversed.size()) {
			cout << reversed[i] << endl;
		}
	}
}