Shared code

/*
AUTHOR : Chandan Agrawal
College : Poornima College of Engg. jaipur, Raj
Mail : chandanagrawal23@gmail.com
*/

#include<bits/stdc++.h>
#include<stdio.h>
using namespace std;

#define fastio ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define MAX 100050

#define ll long long
#define ld long double
#define lli  int

#define pb emplace_back
#define INF 1000000000
#define mod 1000000007

// trignometric function always give value in Radians only
#define PI acos(-1) //3.1415926535897932384626433832795028
#define dsin(degree) sin(degree*(PI/180.0))
#define dcos(degree) cos(degree*(PI/180.0))
#define dtan(degree) tan(degree*(PI/180.0))

#define rsin(radian) sin(radian)
#define rcos(radian) cos(radian)
#define rtan(radian) tan(radian)

#define loop(i,n) for (lli i = 0; i < n; i++)
#define loopitr(xt,vec) for (auto xt : vec)
#define FOR(i,a,b) for (lli i = a; i < b; i+=1)
#define loop_rev(i,n) for (lli i = n-1; i >= 0; i--)
#define FOR_REV(i,a,b) for (lli i = a; i >= b; i--)
#define itr :: iterator it
#define WL(t) while(t --)

#define all(v) v.begin(),v.end()
#define sz(x) int(x.size())
#define F first
#define S second

#define mii map<lli,lli>
#define vi vector<lli>
#define seti set<lli>
#define pii pair<lli,lli>

#define gcd(a,b) __gcd((a),(b))
#define lcm(a,b) (a/gcd(a,b))*b
#define abs(x) ((x < 0)?-(x):x)

template <typename T>
void print(T x){cout<<x<<endl;}
template <typename T1, typename T2>
void print2(T1 x,T2 y){cout<<x<<" "<<y<<endl;}
template <typename T1, typename T2,typename T3>
void print3(T1 x, T2 y,T3 z){cout<<x<<" "<<y<<" "<<z<<endl;}

#define scanarr(a,n) for(lli i=0;i<n;i++)    cin>>a[i];
#define scanvector(a,n) for(lli i=0;i<n;i++){ lli x ; cin>>x; a.pb(x);}

#define printarr(a,n) for(lli i=0;i<n;i++)   cout<<a[i]<<" "; cout<<endl;
#define printvector(vec) for(auto xt : vec) cout<<xt<<" ";    cout<<"\n";
#define printset(st) for(auto xt : st) cout<<xt<<" ";    cout<<"\n";

#define FD(N) fixed<<setprecision(N)

#define endl '\n'

#define deb(x) cout<<#x<<" "<<x<<endl;

// chandan1,2
void chandan1(){int y=1;return;}
void chandan2(){
        loop(i,10){
        lli x=1;
    }
    return(chandan1());
}




void bfs(vi adj[],bool *vis , lli s){
    queue<lli>q;
    q.push(s);
    vis[s]=1;
  //  dist[s]=0;
    while(q.empty()==false){
        lli x = q.front();
        q.pop();
        for(auto xt : adj[x])
            {
                if(!vis[xt])
                {
                    //dist[xt] = dist[x]+1;
                    vis[xt]=1;
                    q.push(xt);
                }
            }
    }

}

int main(){
fastio
lli t=1;
//cin>>t;
chandan2();
while(t--) {
    lli v,e,source,destin;
    cin>>v>>e;
    vi adj[v+1];
    loop(i,e){
        lli x,y;
        cin>>x>>y;
        adj[x].pb(y);
        adj[y].pb(x);
    }
    // connected component count
    lli cc_cnt=0;
    
    bool vis[v+1]={0};
    
    vi ans ;
    FOR(i,1,v+1){
        if(!vis[i]){
            bfs(adj,vis,i);
            cc_cnt++;
            ans.pb(i);
        }
    }
    
    if(cc_cnt==1)
        print(0);
    else{
        print(cc_cnt-1);
        for(lli i=0;i<sz(ans)-1;i++)
            print2(ans[i] , ans[i+1]);
    }
    
}
return 0;
}