#include <cstdio>
#include <cstdlib>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;

#define Nmax 300

int N, M, X, Y, StartComp[Nmax], EndComp[Nmax], L[Nmax], R[Nmax], Comp;
vector<int> G[Nmax], GC[Nmax];
bool Used[Nmax];

int PairUp(int Node)
{
    if(Used[Node]) return 0;
    Used[Node] = 1;
    for(vector<int> :: iterator it = G[Node].begin(); it != G[Node].end(); ++ it)
        if(!R[*it] || PairUp(R[*it]))
        {
            L[Node] = *it;
            R[*it] = Node;
            return 1;
        }
    return 0;
}

void MaxMatching()
{
    int OK = 1;
    while(OK)
    {
        OK = 0;
        memset(Used, 0, sizeof(Used));
        for(int i = 1; i <= N; ++ i)
            if(!L[i] && PairUp(i))
                OK = 1;
    }
}

void DFS(int Node, int Father)
{
    if(GC[Node].size() == 0) EndComp[Comp] = Node;
    if(Father == -1) StartComp[Comp] = Node;
    if(GC[Node].size() == 1) DFS(GC[Node][0], Node);
}

void PrintComp(int Start, int End)
{
    int Node = Start;
    while(GC[Node].size())
    {
        printf("%i ", Node);
        Node = GC[Node][0];
    }
    printf("%i ", End);
}

int main()
{
    freopen("strazi.in", "r", stdin);
    freopen("strazi.out", "w", stdout);

    scanf("%i %i", &N, &M);
    for(int i = 1; i <= M; ++ i)
    {
        scanf("%i %i", &X, &Y);
        G[X].push_back(Y);
    }

    MaxMatching();
    for(int i = 1; i <= N; ++ i)
        if(L[i])
            GC[i].push_back(L[i]);

    vector<int> StartNodes;
    for(int i = 1; i <= N; ++ i)
        if(!R[i])
            StartNodes.push_back(i);

    for(int i = 0; i < StartNodes.size(); ++ i)
    {
        Comp ++;
        DFS(StartNodes[i], -1);
    }

    printf("%i\n", Comp - 1);
    for(int i = 1; i < Comp; ++ i)
        printf("%i %i\n", EndComp[i], StartComp[i + 1]);
    for(int i = 1; i <= Comp; ++ i)
        PrintComp(StartComp[i], EndComp[i]);

    return 0;
}