#pragma GCC optimize("O2,unroll-loops")
#include <iostream>
#include <vector>
using namespace std;
const int maxN = 100001;
struct path{
int to;
int idx;
};
vector<int> pathWeights;
vector<vector<path> > graph(maxN,vector<path>());
//Depth at which it was visited 0 if never
vector<int> visited(maxN,false);
vector<int> xorContinued = {0};
vector<vector<int> > toFlip(32,vector<int>());
//For st-1
int st1Flip = 0;
int st1PathIdx = 0;
int dfs(int currPos, int parent, int depth, int pathId){
//When cycle detection then do my shenanigans with the XOR vector
//Then add to a list that for every bit to xor with contains a list of edges to XOR with
if (visited[currPos]!=0){
// printf("Detected cycle\n");
// printf("Xor continued : ");
// for (int i : xorContinued){
// printf("%d, ",i);
// }
// printf("\n");
//Cycle logic here
//Get all bits that need to be flipped
int startIdx = visited[currPos];
int endIdx = depth;
int beforeStartVal = xorContinued[startIdx];
int lastVal = xorContinued[endIdx];
int bitsToFlip = beforeStartVal ^ lastVal; //Remove bits that are wrongly flipped outside of loop
if (bitsToFlip!=0){
st1Flip = bitsToFlip;
st1PathIdx = pathId;
}
//For each bit to flip we need to add the segment to a list for that bit
// printf("Bits to flip : ");
for (int i = 0;i<31;++i){
if ((bitsToFlip & (1<<i)) != 0){
//Bit is set
toFlip[i].push_back(pathId);
// printf("1");
}
else{
// printf("0");
}
}
// printf("\n");
//Should I change this segments value ? (Yes)
return bitsToFlip;
}
visited[currPos] = depth;
for (int i = 0;i<graph[currPos].size();++i){
path p = graph[currPos][i];
// printf("Visiting %d child of %d\n",p.to,currPos);
if (p.to != parent){
int lastXor = xorContinued[depth]; //Last value in xorContinued
int weight = pathWeights[p.idx-1];
xorContinued.push_back(lastXor ^ weight);
int toFlip = dfs(p.to,currPos,depth+1,p.idx);
if (toFlip!=-1){
// printf("Changing path %d's weight from %d to %d\n",p.idx,weight,weight^toFlip);
pathWeights[p.idx-1] = (weight ^ toFlip);
}
xorContinued.pop_back();
}
}
// visited[currPos] = 0;
return -1;
}
//only doing for subtask 1
int main(){
int nbNodes;
int nbPaths;
scanf("%d %d",&nbNodes,&nbPaths);
for (int i = 0;i<nbPaths;++i){
int from, to, weight;
scanf("%d %d %d",&from, &to, &weight);
pathWeights.push_back(weight);
graph[from].push_back({to,i+1});
graph[to].push_back({from,i+1});
}
dfs(1,0,0,0);
//Not great but i'm tired
int nbFlipping = 0;
for (int i = 0;i<31;++i){
if (!toFlip[i].empty()){
++nbFlipping;
}
}
printf("%d\n",nbFlipping);
if (nbFlipping==0){
return 0;
}
else {
printf("%d 1 %d\n",st1Flip,st1PathIdx);
}
// else{
// for (int i = 0;i<31;++i){
// if (!toFlip[i].empty()){
// printf("%d ",(1<<i));
// printf("%d ",(int)toFlip[i].size());
// for (int j = 0;j<toFlip[i].size();++j){
// printf("%d ",toFlip[i][j]);
// }
// printf("\n");
// }
// }
// }
}
