//In the name of Allah


#include<iostream>
#include<vector>
using namespace std;
const int MAX=100;

vector<int>adj[MAX];

int que[MAX],depth[MAX];
bool mark[MAX];

int bfs(int v,int u){
    int h=0,t=1;
    que[0]=v;
    mark[v]=true;
    for(;h<t;h++){
                  int x=que[h];
                  for(int i=0;i<adj[x].size();i++){
                          if(!mark[adj[x][i]]){
                                               depth[adj[x][i]]=depth[x]+1;
                                               mark[adj[x][i]]=1;
                                               que[t++]=adj[x][i];
                          }
                  }
    }
    return depth[u];
}


int main(){
    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);
    }
    cout<<bfs(1,n)<<endl;
    int x;
    cin>>x;
    
}