#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
using namespace std;

const int MAXN=500005;
const int INF=1e9;
vector<int> adj[MAXN];
int dist[MAXN];
int parent[MAXN];


void bfs(int a, int n){
	
	for(int i=1; i<n+1; i++){
		dist[i]=INF;
		parent[i]=-1;
	}
	
	queue <int> q;
	
	dist[a]=0;
	q.push(a);
	
	
	while(!q.empty()){
		int v=q.front();
		q.pop();
		
		for(int u: adj[v]){
			if(dist[u]==INF){
				dist[u]=dist[v]+1;
				parent[u]=v;
				q.push(u);
			}
		}
	}
}

vector<int> scie(int k){
	if(dist[k]==INF)
	return {};
	
	vector<int> path;
	for(int v=k; v!=-1; v=parent[v])
	path.push_back(v);
	
	reverse(path.begin(), path.end());
	return path;
}


int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
int n,m;
cin>>n>>m;
for(int i=0; i<m; i++){
	int a,b;
	cin>>a>>b;
	adj[a].push_back(b);
	adj[b].push_back(a);
}

int start=1;
int target=n;
bfs(start, target);





	return 0;
}