#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <set>

#define forn(i, n) for(int i = 1; i <= n; ++i)
#define MAX 20001

using namespace std;

vector<vector<int>>graph(MAX);
set <int> b;
map<pair<int, int>, int> table; //чтобы в отсортированном виде

int time[MAX], min_time[MAX];

int n, m, T;

#include <cassert>

/** Begin fast allocation */
const int MAX_MEM = 1e8;
int mpos = 0;
char mem[MAX_MEM];
inline void * operator new ( size_t n ) {
    assert((mpos += n) <= MAX_MEM);
    return (void *)(mem + mpos - n);
}
inline void operator delete ( void * ) noexcept { } // must have!
/** End fast allocation */

void dfs (int v, int p) {
    time[v] = min_time[v] = ++T;
    for (int x : graph[v])
        if (x != p) {
            if (time[x] == 0) { // древесное ребро
                dfs(x, v);
                if (min_time[x] > time[v]) { // мост!
                  b.insert(table[{v, x}]);
                }
                min_time[v] = min(min_time[v], min_time[x]);
            } else { // обратное или двойственное ему ребро в другую сторону
                min_time [v] = min(min_time[v], time [x]);
            }
        }
}


int main() {
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cin >> n >> m;

    int u, v;
    forn(i, m) {
        cin >> v >> u;
        graph[v].push_back(u);
        graph[u].push_back(v);
        table[{v, u}] = i;
    }

    T = 0;
    forn(i, n) if (!time[i]) dfs(i, 0);

    cout << b.size() << "\n";
    for (auto i = b.begin(); i != b.end(); i++) {
        cout << *i << "\n";
    }
}