#ifdef LOCAL
#include <local.hpp>
#else
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2")
#include <bits/stdc++.h>
#define debug(...) ((void)0)
#define postprocess(...) ((void)0)
#endif

using namespace std;
using ll = long long;
using ld = long double;

void solve([[maybe_unused]] int test) {
    int N, M;
    cin >> N >> M;

    bool used[200010] = {};

    vector<int> ans;
    for (int i = 1; i <= M; i++) {
        int u, v;
        cin >> u >> v;
        if (!used[u] && !used[v]) {
            ans.emplace_back(i);
            used[u] = used[v] = true;
        }
    }

    cout << ans.size() << endl;
    for (int i = 0; i < (int)ans.size(); i++) {
        cout << ans[i] << endl;
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    // cin >> t;
    for (int i = 1; i <= t; i++) {
        solve(i);
    }

    postprocess();
}