#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N,M;
vector<int> E[202020];

template<int um> class UF {
	public:
	vector<int> par,rank,cnt;
	UF() {par=rank=vector<int>(um,0); cnt=vector<int>(um,1); for(int i=0;i<um;i++) par[i]=i;}
	void reinit(int num=um) {int i; FOR(i,num) rank[i]=0,cnt[i]=1,par[i]=i;}
	int operator[](int x) {return (par[x]==x)?(x):(par[x] = operator[](par[x]));}
	int count(int x) { return cnt[operator[](x)];}
	int operator()(int x,int y) {
		if((x=operator[](x))==(y=operator[](y))) return x;
		cnt[y]=cnt[x]=cnt[x]+cnt[y];
		if(rank[x]>rank[y]) return par[x]=y;
		rank[x]+=rank[x]==rank[y]; return par[y]=x;
	}
};
UF<202020> uf;
vector<int> C[202020];
int in[202020];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>M;
	
	FOR(i,M) {
		cin>>x>>y;
		E[x-1].push_back(y-1);
		uf(x-1,y-1);
	}
	FOR(i,N) C[uf[i]].push_back(i);
	vector<pair<int,int>> ret;
	FOR(i,N) if(C[i].size()) {
		FORR(c,C[i]) FORR(e,E[c]) in[e]++;
		queue<int> Q;
		FORR(c,C[i]) if(in[c]==0) Q.push(c);
		vector<int> did;
		while(Q.size()) {
			x=Q.front();
			did.push_back(x);
			Q.pop();
			FORR(e,E[x]) {
				if(--in[e]==0) Q.push(e);
			}
		}
		if(did.size()==C[i].size()) {
			FOR(j,did.size()-1) ret.push_back({did[j],did[j+1]});
		}
		else {
			FOR(j,C[i].size()) ret.push_back({C[i][j],C[i][(j+1)%C[i].size()]});
		}
	}
	cout<<ret.size()<<endl;
	FORR(r,ret) cout<<(r.first+1)<<" "<<(r.second+1)<<endl;
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}