#define _USE_MATH_DEFINES
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#include<bits/stdc++.h>
#include<unordered_set>
#include<random>
#include <array>
#include <complex>
#include<chrono>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
#define LP(I,S,G) for (long long int I = (S); I < (G); ++I)
#define IN(X) 	for (int in = 0; in < X.size(); in++)cin >> X[in]
#define OUT(X) 	for (int in = 0; in < X.size(); in++)cout << X[in]<<" "
#define SORT(X) sort((X).begin(), (X).end())
#define CSORT(X,Y) sort(X.begin(), X.end(),Y)
#define COPY(X,Y) copy(X.begin(), X.end(), Y.begin())
#define ALL(X,Y) for (auto &(X) :(Y))
#define FULL(a)  (a).begin(),(a).end()
#define BFS(Q,S) for(Q.push(S);Q.size()!=0;Q.pop())
typedef long long int ll;
typedef unsigned long long int ull;
long long int M = 998244353;

chrono::system_clock::time_point starttime;
using namespace std::chrono;

inline float getTime() {
	return duration_cast<milliseconds>(system_clock::now() - starttime).count();
}


int dx[] = { -1,0,1,0 }, dy[] = { 0,1,0,-1 };

ll MAX(ll A, ll B) { return ((A) > (B) ? (A) : (B)); }
ll MIN(ll A, ll B) { return ((A) < (B) ? (A) : (B)); }
inline long long int xor128() {
	static long long int x = 123456789, y = 362436069, z = 521288629, w = 88675123;
	long long int t = (x ^ (x << 11));
	x = y; y = z; z = w;
	return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}

ll f(ll n, map<ll, ll>& dp) {
	if (dp.find(n) != dp.end())return dp[n];
	dp[n] = f(n / 2, dp) + f(n / 3, dp);
	return dp[n];
}

/*
An undirected, simple connected graph G has n vertices and m edges. The vertices are numbered from 1 to n, and the i-th edge joins the u-th and v-th vertices. Find a subset of edges which form a maximal matching of G.
*/
int main() {
	ll n, m;
	cin >> n >> m;
	vector<vector<ll>> g(n);
	set<ll> s, t, o;
	vector<ll> ans;
	for (int i = 0; i < n; ++i)o.insert(i);
	LP(i, 0, m) {
		ll u, v;
		cin >> u >> v;
		--u, --v;
		if (o.find(u) != o.end() && o.find(v) != o.end()) {
			o.erase(u);
			o.erase(v);
			s.insert(u);
			t.insert(v);
			ans.push_back(i + 1);
		}
	}
	cout << ans.size() << "\n";
	LP(i, 0, ans.size())cout << ans[i] << "\n";
	return 0;
}