#include <iostream>
#include <sstream>
#include <iomanip>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <numeric>
#include <iterator>
#include <functional>
#include <complex>
#include <queue>
#include <stack>
#include <cmath>
#include <cassert>
#include <tuple>
using namespace std;
typedef long long LL;
typedef complex<double> CMP;

class BearSpans { public:
	vector <int> findAnyGraph(int n, int m, int k)
	{
		if(k>29 || (1<<k)>n)
			return vector<int>(1, -1);

		// generate basic
		vector<int> ans = gen_base(1, 1<<k);
		for(int p=1, v=(1<<k)+1; v<=n; p=v++) {
			ans.push_back(p);
			ans.push_back(v);
		}

		vector<vector<bool>> used(n+1, vector<bool>(n+1));
		for(int i=0; i<ans.size(); i+=2) {
			used[ans[i]][ans[i+1]] = true;
			used[ans[i+1]][ans[i]] = true;
		}

		for(int s=1; s<=n && ans.size()<2*m; ++s)
		for(int e=s+1; e<=n && ans.size()<2*m; ++e)
			if(!used[s][e]) {
				ans.push_back(s);
				ans.push_back(e);
			}

		return ans;
	}

	vector<int> gen_base(int vS, int vE)
	{
		if(vS+1 == vE) {
			vector<int> ans;
			ans.push_back(vS);
			ans.push_back(vE);
			return ans;
		}

		int vM1 = vS + (vE-vS+1)/2 -1;
		int vM2 = vS + (vE-vS+1)/2;
		vector<int> a = gen_base(vS, vM1);
		vector<int> b = gen_base(vM2, vE);
		a.insert(a.end(), b.begin(), b.end());
		a.push_back(vM1);
		a.push_back(vM2);
		return a;
	}
};

// BEGIN CUT HERE
struct UnionFind
{
	vector<int> uf, sz;
	int nc;

	UnionFind(int N): uf(N), sz(N,1), nc(N)
		{ for(int i=0; i<N; ++i) uf[i] = i; }
	int size()
		{ return nc; }
	int size(int a)
		{ return sz[Find(a)]; }
	int Find(int a)
		{ return uf[a]==a ? a : uf[a]=Find(uf[a]); }
		// Semi-compression w.o. recursion.
		//{ while(uf[a] != a) a=uf[a]=uf[uf[a]]; return a; }
	bool Union(int a, int b)
		{
			a = Find(a);
			b = Find(b);
			if( a != b )
			{
				if( sz[a] >= sz[b] ) swap(a, b);
				uf[a] = b;
				sz[b] += sz[a];
				--nc;
			}
			return (a!=b);
		}
};

int verify(vector<int> ans)
{
	int m = ans.size() / 2;
	int n = *max_element(ans.begin(), ans.end());
	if(n == -1)
		return -1;
	vector<tuple<int,int,int>> cft;
	for(int i=0; i<m; ++i)
		cft.emplace_back(i+1, ans[2*i+0]-1, ans[2*i+1]-1);
	vector<bool> added(cft.size());

	UnionFind uf(n);
	int LoopCount=0;
	while(uf.size() > 1) {
		vector<int> to_add;
		vector<bool> done(n);

		for(int e=0; e<cft.size(); ++e) if(!added[e]) {
			int a = uf.Find(get<1>(cft[e]));
			int b = uf.Find(get<2>(cft[e]));
			if(a!=b) {
				if(!done[a] || !done[b]) {
					to_add.push_back(e);
					done[a] = true;
					done[b] = true;
				}
			}
		}

		for(int e: to_add) {
			added[e] = true;
			uf.Union(get<1>(cft[e]), get<2>(cft[e]));
		}

		LoopCount++;
	}
	return LoopCount;
}

#include <ctime>
double start_time; string timer()
 { ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
 { os << "{ ";
   for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
   os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
void verify_case(const vector <int>& Expected, const vector <int>& Received) {

 bool ok = (verify(Expected) == verify(Received));
 if(ok) cerr << "PASSED" << timer() << endl;  else { cerr << "FAILED" << timer() << endl;
 cerr << "\to: " << Expected << endl << "\tx: " << Received << endl; } }
#define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
#define END	 verify_case(_, BearSpans().findAnyGraph(n, m, k));}
int main(){

CASE(0)
	int n = 17; 
	int m = 22; 
	int k = 1; 
	int __[] = {1, 2, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7, 1, 8, 1, 9, 1, 10, 1, 11, 1, 12, 1, 13, 1, 14, 1, 15, 1, 16, 1, 17, 2, 3, 2, 8, 3, 9, 8, 9, 10, 12, 12, 14 };
	  vector <int> _(__, __+sizeof(__)/sizeof(*__)); 
END
CASE(1)
	int n = 9; 
	int m = 12; 
	int k = 3; 
	int __[] = {6, 5, 7, 6, 1, 2, 3, 4, 8, 9, 3, 5, 7, 4, 1, 9, 6, 2, 6, 1, 1, 8, 4, 5 };
	  vector <int> _(__, __+sizeof(__)/sizeof(*__)); 
END
CASE(2)
	int n = 9; 
	int m = 12; 
	int k = 7; 
	int __[] = {-1 };
	  vector <int> _(__, __+sizeof(__)/sizeof(*__)); 
END
CASE(3)
	int n = 1000; 
	int m = 999; 
	int k = 970; 
	int __[] = {-1 };
	  vector <int> _(__, __+sizeof(__)/sizeof(*__)); 
END
CASE(4)
	int n = 2; 
	int m = 1; 
	int k = 1; 
	int __[] = {1, 2 };
	  vector <int> _(__, __+sizeof(__)/sizeof(*__)); 
END
CASE(5)
	int n = 3; 
	int m = 2; 
	int k = 1; 
	int __[] = {1, 2, 1, 3 };
	  vector <int> _(__, __+sizeof(__)/sizeof(*__)); 
END
CASE(6)
	int n = 3; 
	int m = 3; 
	int k = 2; 
	int __[] = {-1 };
	  vector <int> _(__, __+sizeof(__)/sizeof(*__)); 
END
/*
CASE(7)
	int n = ; 
	int m = ; 
	int k = ; 
	int __[] = ;
	  vector <int> _(__, __+sizeof(__)/sizeof(*__)); 
END
CASE(8)
	int n = ; 
	int m = ; 
	int k = ; 
	int __[] = ;
	  vector <int> _(__, __+sizeof(__)/sizeof(*__)); 
END
*/

}
// END CUT HERE
