#define PROBLEM "https://judge.yosupo.jp/problem/general_matching"

#include <bits/stdc++.h>

#pragma GCC optimize("Ofast,unroll-loops")

#include "blazingio/blazingio.min.hpp"

#include "cp-algo/linalg/matrix.hpp"

using namespace std;

using namespace cp_algo::math;

using namespace cp_algo::linalg;

using namespace cp_algo::random;

const int64_t mod = 998244353;

using base = modint<mod>;

void solve() {

int n, m;

cin >> n >> m;

matrix<base> T(n);

for(int i = 0; i < m; i++) {

int u, v;

cin >> u >> v;

base x = rng();

T[u][v] += x;

T[v][u] -= x;

}

auto [pivots, free] = matrix(T).echelonize();

matrix<base> B(size(pivots));

for(int i = 0; i < ssize(pivots); i++) {

for(int j = 0; j < ssize(pivots); j++) {

B[i][j] = T[pivots[i]][pivots[j]];

}

}

B = B.inv().second;

vector<pair<int, int>> ans;

for(size_t i = 0; i < size(pivots); i++) {

for(size_t j = 0; j < size(pivots); j++) {

if(T[pivots[i]][pivots[j]] != 0 && B[i][j] != 0) {

ans.emplace_back(pivots[i], pivots[j]);

B.eliminate<gauss_mode::reverse>(i, j);

B.eliminate<gauss_mode::reverse>(j, i);

B.normalize();

for(int k = 0; k < ssize(pivots); k++) {

B[i][k] = B[j][k] = 0;

}

}

}

}

cout << size(ans) << "\n";

for(auto [u, v]: ans) {

cout << u << ' ' << v << "\n";

}

}

signed main() {

//freopen("input.txt", "r", stdin);

ios::sync_with_stdio(0);

cin.tie(0);

int t = 1;

// cin >> t;

while(t--) {

solve();

}

}