#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 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));
  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;
  while (1) {
    queue<int> Q; Q.push(s);
    vector<int> prev(n, -1); prev[s] = s;
    while (!Q.empty() && prev[t] < 0) {
      int u = Q.front(); Q.pop();
      for (Edges::const_iterator e = g[u].begin(), eEnd = g[u].end(); e != eEnd; ++e) if (prev[e->dst] < 0 && RESIDUE(u, e->dst) > 0) {
        prev[e->dst] = u;
        Q.push(e->dst);
      }
    }
    if (prev[t] < 0) return total; // prev[x] == -1 <=> t-side
    Weight inc = INF;
    for (int j = t; prev[j] != j; j = prev[j])
      inc = min(inc, RESIDUE(prev[j], j));
    for (int j = t; prev[j] != j; j = prev[j])
      flow[prev[j]][j] += inc, flow[j][prev[j]] -= inc;
    total += inc;
  }
}

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;
		}
	}
}