мосты

#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <map>
#define pii pair <int,int>
#define vec vector
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
void cv(vector <int> &v){
    for (auto x: v) cout<< (x+1) <<' ';
    cout<<"\n";
}

void cvl(vector <ll> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}


void cvv(vector <vector <int> > &v){
    for (auto x: v) cv(x);
    cout<<"\n";
}

void cvb(vector <bool> v){
    for (bool x: v) cout<<x<<' ';
    cout<<"\n";
}

void cvs(vector <string>  v){
    for (auto a: v){
        cout<<a<<"\n";
    }
}

void cvp(vector <pii> a){
    for (auto p: a){
        cout<<p.first<<' '<<p.second<<"\n";
    }
    cout<<"\n";
}

int n,m;
vector <int> clr, dp, mndp,  ans;

vector <vector <int> > G;

map <pii, int> ed;

void dfs(int v, int pr){
    clr[v] = 1;
    if (pr != -1){
        dp[v] = dp[pr] + 1;
    }
    for (int u: G[v]){
        if (u != pr && clr[u] == 0){
            dfs(u, v);
        }
        mndp[v] = min(mndp[v], mndp[u]);
        if (dp[v] < mndp[u]){
            ans.push_back(ed[{min(v,u), max(v,u)}]);
        }
    }
    clr[v] = 2;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>m;
    G.assign(n, vector <int> (0));
    clr.assign(n, 0);
    dp.resize(n);
    mndp.resize(n);
    for (int i = 0; i < m; ++i){
        int a,b;
        cin>>a>>b; a--; b--;
        ed[{min(a,b), max(a,b)}] = i;
        G[a].push_back(b);
        G[b].push_back(a);
    }
    for (int i = 0; i < n; ++i){
        if (clr[i] == 0){
            dp[i] = 0;
            dfs(i, -1);
        }
    }
    sort(ans.begin(), ans.end());
    cout<<ans.size()<<"\n";
    cv(ans);
}