#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>

using namespace std;

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

bool u[20005];
vector<edge> g[20005];
vector<edge> g2[20004];

void deik(int st, long long* d)
{
	memset(u, 0, sizeof(u));
	for(int i = 0; i < 20005; i++)
		d[i] = -1;

	d[st]=  0;
	set<pair<long long, int> > s;
	s.insert(make_pair(d[st], st));
	while(s.size() > 0)
	{
		int v = s.begin()->second;
		s.erase(s.begin());
		u[v] = 1;
		for(int i = 0; i < g[v].size(); i++)
		{
			int to = g[v][i].to, w = g[v][i].w;
			if(!u[to] && (d[to] < 0 || d[to] > d[v] + w))
			{
				s.erase(make_pair(d[to], to));
				d[to] = d[v] + w;
				s.insert(make_pair(d[to], to));
			}
		}
	}
}

long long d[2][20005];
int tin[20005];
int real[20005];
int tme = 1;
bool ans[100005];

void dfs(int v, int p = -1)
{
	u[v] = 1;
	tin[v] = real[v] = tme ++;
	for(int i = 0; i < g2[v].size(); i++)
	{
		int to = g2[v][i].to;
		if(to == p)
			continue;
		if(u[to])
			real[v] = min(real[v], tin[to]);
		else
		{
			dfs(to, v);
			real[v] = min(real[v], real[to]);
		}
		if(tin[v] < real[to])
			ans[g2[v][i].id] = 1;
	}
}

int main()
{
	int n, m;
	scanf("%d%d", &n, &m);

	for(int i = 0; i < m; i++)
	{
		int a, b, w;
		scanf("%d%d%d", &a, &b, &w);
		--a, --b;
		g[a].push_back(edge(b, w, i));
		g[b].push_back(edge(a, w, i));
	}

	deik(0, d[0]);
	deik(n - 1, d[1]);

	for(int i = 0; i < n; i++)
	{
		for(int j = 0; j < g[i].size(); j++)
		{
			int to = g[i][j].to;
			if(d[0][i] + d[1][to] + g[i][j].w == d[0][n-1] || d[1][i] + d[0][to] + g[i][j].w == d[0][n-1])
				g2[i].push_back(g[i][j]);
		}
	}

	memset(u, 0, sizeof(u));
	dfs(0);
	int cnt = 0;
	for(int i = 0; i < m; i++)
		cnt += ans[i];

	printf("%d\n", cnt);
	for(int i = 0; i < m; i++)
		if(ans[i])
			printf("%d ", i + 1);
	printf("\n");

	return 0;
}