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

#define pb push_back

using namespace std;

typedef pair <int, int> PII; 

const int maxN = 1000 * 1000 + 5;

int root[maxN];
int h[maxN];

int getroot(int x) { return x == root[x] ? x : (root[x] = getroot(root[x]));}
bool join(int u, int v) // union
{
	u = getroot(u); v = getroot(v);
	if (u == v) return 0;
	if (h[u] > h[v]) swap(u, v);
	root[u] = v;
	h[v] = max(h[v], h[u] + 1);
	return 1;
}

int main()
{
	int n, m, k;
	vector <PII> edge;
	scanf("%d%d%d", &n, &m, &k);
	for (int i = 0; i < n; i++)
		root[i] = i;
	for (int i = 0; i < m; i++)
	{
		int u, v;
		scanf("%d%d", &u, &v);
		u--; v--;  // 0 base
		if (u > v) swap(u, v);
		if (u > k - 1)
			join(u, v); // yal hayi ke u > k-1 va v > k-1 ro dar nazar migirim
		else
			edge.pb(make_pair(u, v));
	}
	vector <PII> ans;
	for (int i = 0; i < (int)edge.size(); i++)
		if (!join(edge[i].first, edge[i].second)) // agar dor be vojood mioomad yal ra hazv mikonim
			ans.pb(edge[i]);
	printf("%d\n", ans.size());
	for (int i = 0; i < (int)ans.size(); i++)
		printf("%d %d\n", ans[i].first+1, ans[i].second+1);
	return 0;
}