#include <bits/stdc++.h>

using namespace std;

#define sz(x) int(x.size())
#define all(x) begin(x),end(x)
#define forsn(i,s,n) for(int i=int(s);i<int(n);i++)
#define forn(i,n) for(int i=0;i<int(n);i++)
#define dforsn(i,s,n) for(int i=int(n)-1;i>=int(s);i--)
#define dforn(i,n) for(int i=int(n)-1;i>=0;i--)
#define dbg(x) cerr<<#x<<": "<<x<<endl

#define fst first
#define snd second
#define pb push_back
#define eb emplace_back

typedef pair<int,int> ii;
typedef vector<ii> vii;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<int> vi;

//const int MAXN = 2e5+5;
//const ll INF = 1e18;
const int MOD = 1e9+7;

template<class x> ostream & operator<<(ostream & out, vector<x> v){
    out<<"[ ";
    for(auto y : v) out<<y<<" ";
    out<<"]";
    return out;
}

template<class a, class b> ostream & operator<<(ostream & out, pair<a, b> p){
    return out<<"("<<p.fst<<", "<<p.snd<<")";
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    
    int n,m;
    cin>>n>>m;
    vector<vi> adj(n,vi(n,0));
    vi deg(n,0);
    forn(i,m){
        int u,v;
        cin>>u>>v;
        --u,--v;
        adj[u][v]=adj[v][u]=1;
        deg[u]++,deg[v]++;
    }
    vi p(n);
    iota(all(p),0);
    sort(all(p),[&](int u, int v){ return deg[u]<deg[v]; });
    if(deg[p[n-1]]-deg[p[n-2]]>=5){
        cout<<"ok\n";
        return 0;
    }
    vii edges;
    int k=0;
    forn(i,n) if(!adj[i][p[n-1]]){
        edges.eb(i,p[n-1]);
        if(++k==5) break;
    }
    cout<<k<<'\n';
    forn(i,k) cout<<edges[i].fst+1<<' '<<edges[i].snd+1<<'\n';
    
    return 0;
}