#include<algorithm>
#include<bitset>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<deque>
#include<fstream>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<utility>
#include<vector>

using namespace std;

typedef long long int lld;
typedef pair<int,int> PII;

const int INF = (1<<31)-1;
const lld LINF = (1LL<<63)-1;

const int NMAX = 100000+5;
const int MMAX = 100000+5;
const int KMAX = 100000+5;
const int PMAX = 100000+5;
const int LMAX = 100000+5;
const int VMAX = 100000+5;

int K,N,M,i,j;

int main()
{
    //freopen("input.txt","r",stdin);
    //freopen("output.txt","w",stdout);

    scanf("%d%d%d",&K,&N,&M);

    if(N==K)
    {
        printf("%d\n",K*(K-1)/2-(M-1));
        for(i=N; i<=K; i++)
            printf("%d %d\n",1,i);
        for(i=2; i<=N; i++)
            for(j=i+1; j<=N; j++)
                printf("%d %d\n",i,j);
    }
    else if(M==K)
    {
        printf("%d\n",N-1);
        for(i=2; i<=N-1; i++)
            printf("%d %d",1,i);
    }
    else
    {
        printf("-1\n");
    }


    return 0;
}