import std.stdio, std.array, std.string, std.conv, std.algorithm;
import std.typecons, std.range, std.random, std.math, std.container;
import std.numeric, std.bigint, core.bitop, core.stdc.string;

void main() {
    auto s = readln.split.map!(to!int);
    auto N = s[0];
    auto M = s[1];
    auto E = M.iota.map!(_ => readln.split.map!(x => x.to!int-1).array).array;
    s = readln.split.map!(to!int);
    auto S = s[0]-1;
    auto T = s[1]-1;

    auto FF = new FordFulkerson(N, S, T);
    foreach (e; E) FF.add_edge(e[0], e[1], 1), FF.add_edge(e[1], e[0], 1);

    FF.run.writeln;

    int[] ans;
    foreach (i; 0..M) {
        int u = E[i][0];
        int v = E[i][1];
        if (FF.flow[u][v]) ans ~= i + 1;
    }

    ans.length.writeln;
    ans.each!writeln;
}


class FordFulkerson {
    int N, source, sink;
    int[][] adj;
    int[][] flow;
    bool[] used;

    this(int n, int s, int t) {
        N = n;
        source = s;
        sink = t;
        assert (s >= 0 && s < N && t >= 0 && t < N);
        adj = new int[][](N);
        flow = new int[][](N, N);
        used = new bool[](N);
    }

    void add_edge(int from, int to, int cap) {
        adj[from] ~= to;
        adj[to] ~= from;
        flow[from][to] = cap;
    }

    int dfs(int v, int min_cap) {
        if (v == sink)
            return min_cap;
        if (used[v])
            return 0;
        used[v] = true;
        foreach (to; adj[v]) {
            if (!used[to] && flow[v][to] > 0) {
                auto bottleneck = dfs(to, min(min_cap, flow[v][to]));
                if (bottleneck == 0) continue;
                flow[v][to] -= bottleneck;
                flow[to][v] += bottleneck;
                return bottleneck;
            }
        }
        return 0;
    }

    int run() {
        int ret = 0;
        while (true) {
            foreach (i; 0..N) used[i] = false;
            int f = dfs(source, int.max);
            if (f > 0)
                ret += f;
            else
                return ret;
        }
    }
}

