#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // maximal?
  int n, m;
  cin >> n >> m;
  VVI to(n);
  vector<char> used(n);
  VI ans;
  rep(i, m) {
    int u, v;
    cin >> u >> v;
    u--, v--;
    if (!used[u] && !used[v]) {
      used[u] = used[v] = true;
      ans.emplace_back(i);
    }
  }
  cout << ans.size() << '\n';
  for (int i : ans) cout << i + 1 << '\n';
}