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4.Message_Routes.cpp
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4.Message_Routes.cpp
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#include <bits/stdc++.h>
using namespace std;
#define pii pair<int,int>
#define int64 int64_t
#define IOS ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define ll long long
#define pb push_back
#define str string
#define ri(x) int x;cin>>x;
#define rl(x) ll x; cin>>x;
#define rs(x) str x; cin>>x;
#define rd(x) d x; cin>>x;
#define w(x) cout<<x;
#define vec(x) std::vector<x>
#define nl '\n'
#define all(x) x.begin(),x.end()
#define map_traverse(it,x) for(auto it = BN(x); it!= ED(x); it++)
#define debug(x) for(auto y : x) {cout<<y<<" ";} cout<<nl;
#define PI 3.14159265358979323846264338327950L
#define rep(i,a,b) for(int i=a;i<b;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
const unsigned int M = 1000000007;
const int mxN=2e5;
const int N = 100031;
const int nax = 1e5+5;
vector<int > g[nax] , par(nax,0);
void solve(){
int n,m;
cin>>n>>m;
// vec(vec(int))g;vec(int)par(mxN,0);
rep(i,0,m){
int a,b; cin>>a>>b;
g[a].pb(b); g[b].pb(a);
}
// cout<<"hello";
queue<int>q;
q.push(1); par[1]=-1;
while(!q.empty()){
int p = q.front(); q.pop();
for(auto x:g[p]){
if(!par[x]){
q.push(x);
par[x]=p;
}
}
}
if(par[n]){
stack<int>st;
int p = par[n];
st.push(n);
while(p!=-1){
st.push(p);
p = par[p];
}
cout<<st.size()<<nl;
while(!st.empty()){
cout<<st.top()<<" ";
st.pop();
}
}else{
cout<<"IMPOSSIBLE"<<nl;
}
}
int main()
{
IOS;
// int t; cin>>t;
// while (t--)
// {
// solve();
// }
solve();
}