#include <stdio.h>
#include <bits/stdc++.h>
#include <algorithm>
#define bal printf("a");
using namespace std;
typedef struct pairs {
    int i, j;
} paira;
typedef struct node_t {
    int index, count;
} nodes;
bool cmp (nodes a, nodes b) {
    return a.count < b.count;
}
vector <paira> araa;

int maps[40][40];
int main () {
    int n, k, i;
    scanf("%d %d", &n, &k);
    nodes ara[50];
    for (i=0; i<n; i++) {
        ara[i].index = i+1;
        ara[i].count = 0;
    }
    int counts[40];
    for (i=0; i<40; i++) counts[i] = 0;
    for (i=1; i<=n; i++) {
        while (counts[i] < k+1) {
            sort (ara, ara+n, cmp);
            paira temp;
            int j=0, y;
            y = ara[j].index;
            while (i==y || maps[i][y]) {
                j++;
                y = ara[j].index;
            }
            if (y < i) {
                temp.i = y;
                temp.j = i;
            }
            else {
                temp.i = i;
                temp.j = y;
            }
            counts[i]++;
            counts[y]++;
            for (int z = 0; z<n; z++) if (ara[z].index == i) ara[z].count = counts[i];
            for (int z = 0; z<n; z++) if (ara[z].index == y) ara[z].count = counts[y];
            maps[i][y] = maps[y][i] = 1;
            araa.push_back(temp);
        }
    }
    printf("%d\n", araa.size());
    for (i=0; i<araa.size(); i++) printf("%d %d\n", araa[i].i, araa[i].j);

    return 0;
}





#include <cstdio>
#include <cmath>
#define PI 2*asin(1)
int main () {
    int n;
    scanf("%d", &n);
    double ara[n];
    int i;
    double sum=0;
    for (i=0; i<n; i++) {
        scanf("%lf", &ara[i]);
        sum += ara[i];
    }

    double r, theta;
    theta = ara[0]/sum;

    theta = theta * 2*PI;
    int flag = 1;
    double radius = (double(ara[0]))/(2.0*sin(theta));
    for (i=0; i<n && flag; i++) {
        theta = ara[i]/sum;
        theta = theta * 2.0*PI;
        r = ara[i]/(2.0*sin(theta/2.0));
        printf("%lf %lf\n", radius, r);
        if (fabs(r-radius) > 1e-6) flag = 0;
    }
    if (flag) printf("%.9lf\n", radius);
    else printf("-1\n");
    return 0;
}