#include<bits/stdc++.h>
using namespace std;
int32_t main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n,m,k;
cin >> n >> m >> k;
vector<array<int,2>> ans;
int yes = 1;
vector<int> in(n,0);
vector<int> a[n];
while(m--)
{
int u,v;
cin >> u >> v;
ans.push_back({u,v});
in[v]++;
a[u].push_back(v);
}
queue<int> q;
vector<int> cur;
vector<int> vis(n,0);
for(int i=0;i<n;i++)
{
if(in[i]==0)
{
q.push(i);
vis[i] = 1;
}
if(a[i].size()==0) cur.push_back(i);
}
while(q.size())
{
int s = q.front();
q.pop();
int ok = 0;
for(int x:a[s])
{
// cout << s << " "<< x << " "<< vis[x] << endl;
ok = 1;
if(vis[x]) continue;
vis[x] = 1;
q.push(x);
}
}
for(int i=0;i<n;i++)
{
if(vis[i]==0 || a[i].size()>=2) yes = 0;
vis[i] = 0;
}
for(int i=0;i<cur.size()-1;i++)
{
a[cur[i]].push_back(cur[i+1]);
in[cur[i+1]]++;
ans.push_back({cur[i],cur[i+1]});
}
for(int i=0;i<n;i++)
{
if(in[i]==0)
{
q.push(i);
vis[i] = 1;
}
if(a[i].size()==0) cur.push_back(i);
}
while(q.size())
{
int s = q.front();
q.pop();
int ok = 0;
for(int x:a[s])
{
// cout << s << " "<< x << " "<< vis[x] << endl;
ok = 1;
if(vis[x]) continue;
vis[x] = 1;
q.push(x);
}
}
for(int i=0;i<n;i++)
{
if(vis[i]==0 || a[i].size()>=2) yes = 0;
vis[i] = 0;
}
if(yes==0 || ans.size()!=n-1)
{
cout << "NO" << endl;
return 0;
}
for(auto x:ans) cout << x[0] << " "<< x[1] << endl;
}
