#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define R cin>>
#define ll long long
#define ln cout<<'\n'
#define in(a) insert(a)
#define pb(a) push_back(a)
#define pd(a) printf("%.10f\n",a)
#define mem(a) memset(a,0,sizeof(a))
#define all(c) (c).begin(),(c).end()
#define iter(c) __typeof((c).begin())
#define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
#define rep(i,n) REP(i,0,n)
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}void pr(){ln;}
template<class A,class...B>void pr(const A &a,const B&...b){cout<<a<<(sizeof...(b)?" ":"");pr(b...);}
template<class A>void PR(A a,ll n){rep(i,n)cout<<(i?" ":"")<<a[i];ln;}
const ll MAX=1e9+7,MAXL=1LL<<61,dx[8]={-1,0,1,0,-1,-1,1,1},dy[8]={0,1,0,-1,-1,1,1,-1};
typedef pair<ll,ll> P;

#define N 200001
vector<int> G[N],rG[N],g;
int n,cmp[N],u[N];

void add_edge(int x,int y){G[x].push_back(y);rG[y].push_back(x);}
void dfs(int x){u[x]=1;rep(i,G[x].size())if(!u[G[x][i]])dfs(G[x][i]);g.push_back(x);} 
void rdfs(int x,int k){u[x]=1;cmp[x]=k;rep(i,rG[x].size())if(!u[rG[x][i]])rdfs(rG[x][i],k);}
int scc() {
  fill(u,u+n,0);g.clear();rep(i,n)if(!u[i])dfs(i);fill(u,u+n,0);
  int k=0;rrep(i,g.size())if(!u[g[i]])rdfs(g[i],k++);return k;
}

int p[200001],r[200001];
void init(){rep(i,200001)p[i]=i,r[i]=0;}
int find(int x){return (p[x]==x)?x:(p[x]=find(p[x]));}
void unite(int x,int y) {
  x=find(x),y=find(y);
  if(x==y)return;
  if(r[x]<r[y])p[x]=y;
  else{p[y]=x;if(r[x]==r[y])r[x]++;}
}
bool same(int x,int y){return find(x)==find(y);}

void Main() {
  init();
  ll m;
  cin >> n >> m;
  rep(i,m) {
    ll x,y;
    cin >> x >> y;
    x--,y--;
    add_edge(x,y);
    unite(x,y);
  }
  scc();
  P a[n];
  rep(i,n) a[i]=P(cmp[i],i);
  sort(a,a+n);
  set<ll> s[n];
  vector<ll> v[n];
  rep(i,n) {
    v[find(a[i].S)].pb(a[i].S);
    s[find(a[i].S)].in(a[i].F);
  }
  vector<P> ans;
  rep(i,n) {
    rep(j,(ll)v[i].size()-1) ans.pb(P(v[i][j]+1,v[i][j+1]+1));
    if(s[i].size()!=v[i].size()) ans.pb(P(v[i].back()+1,v[i][0]+1));
  }
  pr(ans.size());
  rep(i,ans.size()) pr(ans[i].F,ans[i].S);
}

int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}