#include <iostream>
#include <fstream>
#include <cstdio>
#include <sstream>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <string>
#include <map>
#include <vector>
#include <set>
#include <queue>
#include <deque>
#include <ctime>
#include <cstdlib>

using namespace std;

#define sz(x) ((int)((x).size()))

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;

const double EPS = 1e-9;
const double PI = acos(-1.0);

const int MAXN = (int)(2e5) + 10;
const ll INF = (ll)(1e18);

struct Edge {
	int to, w, id;

	Edge(int to = 0, int w = 0, int id = 0) : to(to), w(w), id(id) {}
};

int n, m;
vector<Edge> g[MAXN];
ll di[MAXN];
int ans[MAXN], na;
int good[MAXN];
int tin[MAXN], tout[MAXN], timer;
bool used[MAXN];

int go(int v) {
	if (good[v] != -1)
		return good[v];
	good[v] = 0;
	for (int i = 0; i < sz(g[v]); i++) {
		Edge e = g[v][i];
		if (di[e.to] == di[v] + e.w) {
			if (go(e.to) == 1) {
				good[v] = 1;
			}
		}
	}
	return good[v];
}

void go1(int v, int pr = -1) {
	used[v] = true;
	tin[v] = tout[v] = timer++;
	for (int i = 0; i < sz(g[v]); i++) {
		Edge e = g[v][i];
		if (e.to == pr)
			continue;
		if (di[e.to] != di[v] + e.w && di[e.to] != di[v] - e.w) {
			continue;
		}
		if (used[e.to]) {
			tout[v] = min(tout[v], tin[e.to]);
		} else {
			go1(e.to, v);
			tout[v] = min(tout[v], tout[e.to]);
			if (tout[e.to] > tin[v]) {
				if (di[e.to] == di[v] + e.w && good[v] == 1 && good[e.to] == 1) {
					ans[na++] = e.id;
				}
			}
		}
	}
}

int main() {
	//freopen(".in", "r", stdin);
	//freopen(".out", "w", stdout);

	scanf("%d%d", &n, &m);
	for (int i = 0; i < m; i++) {
		int v, u, w;
		scanf("%d%d%d", &v, &u, &w);
		--v;
		--u;
		g[v].push_back(Edge(u, w, i));
		g[u].push_back(Edge(v, w, i));
	}
	for (int i = 0; i < n; i++) {
		di[i] = INF;
	}
	di[0] = 0;
	set<pii> st;
	st.insert(make_pair(di[0], 0));
	while (!st.empty()) {
		int v = st.begin()->second;
		st.erase(st.begin());
		for (int i = 0; i < sz(g[v]); i++) {
			Edge e = g[v][i];
			if (di[e.to] > di[v] + e.w) {
				st.erase(make_pair(di[e.to], e.to));
				di[e.to] = di[v] + e.w;
				st.insert(make_pair(di[e.to], e.to));
			}
		}
	}
	for (int i = 0; i < n; i++) {
		good[i] = -1;
	}
	good[n - 1] = 1;
	go(0);
	for (int i = 0; i < n; i++) {
		if (!used[i]) {
			go1(i);
		}
	}
	sort(ans, ans + na);
	na = (int)(unique(ans, ans + na) - ans);
	printf("%d\n", na);
	for (int i = 0; i < na; i++) {
		printf("%d%c", ans[i] + 1, " \n"[i == na - 1]);
	}

	return 0;
}
