#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
using ll = long long;

#include<atcoder/scc>
#include<atcoder/dsu>
int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int n,m;
    cin>>n>>m;
    vector<int> u(m),v(m);
    atcoder::scc_graph g(n);
    for(int i = 0;i<m;i++){
        cin>>u[i]>>v[i];
        u[i]--;v[i]--;
        g.add_edge(u[i],v[i]);
    }
    auto use = g.scc();
    vector<pair<int,int>> ans;
    vector<int> cnt(n,0);
    for(int i = 0;i<use.size();i++) for(int j:use[i]) cnt[j] = i;
    // for(int i = 0;i<use.size();i++){
    //     int m = use[i].size();
    //     if(m==1) continue;
    //     for(int j = 0;j<m;j++){
    //         int nj = (j+1) % m;
    //         ans.push_back(make_pair(use[i][j],use[i][nj]));
    //     }
    // }
    int mm = use.size();
    atcoder::dsu uf(mm);
    for(int i = 0;i<m;i++) uf.merge(cnt[u[i]],cnt[v[i]]);
    for(auto&now:uf.groups()){
        sort(now.begin(),now.end());
        bool fn = false;
        vector<int> can;
        for(int i = 0;i<now.size();i++){
            int ni = now[i];
            for(int j:use[ni]){
                can.push_back(j);
            }
            if(use[ni].size()>1) fn = true;
        }
        for(int i = 0;i+1<can.size();i++) ans.push_back(make_pair(can[i],can[i+1]));
        if(fn) ans.push_back(make_pair(can.back(),can[0]));
        //for(int i = 0;i+1<now.size();i++) ans.push_back(make_pair(use[now[i]][0],use[now[i+1]][0]));
    }
    cout<<ans.size()<<endl;
    for(int i = 0;i<ans.size();i++) cout<<ans[i].first+1<<" "<<ans[i].second+1<<endl;
}