#include <bits/stdc++.h>
using namespace std;
const int N = 1e3;
namespace fastinput {
inline int readChar();
template <class T = int>
inline T readInt();
template <class T>
inline void writeInt(T x, char end = 0);
inline void writeChar(int x);
inline void writeWord(const char *s);
static const int buf_size = 4096;
inline int getChar() {
  static char buf[buf_size];
  static int len = 0, pos = 0;
  if (pos == len) pos = 0, len = fread(buf, 1, buf_size, stdin);
  if (pos == len) return -1;
  return buf[pos++];
}
inline int readChar() {
  int c = getChar();
  while (c <= 32) c = getChar();
  return c;
}
template <class T>
inline T readInt() {
  int s = 1, c = readChar();
  T x = 0;
  if (c == '-') s = -1, c = getChar();
  while ('0' <= c && c <= '9') x = x * 10 + c - '0', c = getChar();
  return s == 1 ? x : -x;
}
static int write_pos = 0;
static char write_buf[buf_size];
inline void writeChar(int x) {
  if (write_pos == buf_size)
    fwrite(write_buf, 1, buf_size, stdout), write_pos = 0;
  write_buf[write_pos++] = x;
}
template <class T>
inline void writeInt(T x, char end) {
  if (x < 0) writeChar('-'), x = -x;
  char s[24];
  int n = 0;
  while (x || !n) s[n++] = '0' + x % 10, x /= 10;
  while (n--) writeChar(s[n]);
  if (end) writeChar(end);
}
inline void writeWord(const char *s) {
  while (*s) writeChar(*s++);
}
struct Flusher {
  ~Flusher() {
    if (write_pos) fwrite(write_buf, 1, write_pos, stdout), write_pos = 0;
  }
} flusher;
}  // namespace fastinput
using namespace fastinput;
int main() {
  ::ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, k;
  n = readInt();
  k = readInt();
  vector<pair<int, int> > v;
  for (int i = 0; i < n; ++i) {
    int a, b;
    a = readInt();
    b = readInt();
    v.push_back(pair<int, int>(a, -1));
    v.push_back(pair<int, int>(b, 1));
  }
  sort(v.begin(), v.end());
  int cnt = 0;
  vector<int> ans;
  for (auto x : v) {
    if (x.second == -1) {
      ++cnt;
      if (cnt == k) ans.push_back(x.first);
    } else {
      if (cnt == k) ans.push_back(x.first);
      --cnt;
    }
  }
  printf("%d\n", ans.size() / 2);
  for (int i = 0; 2 * i < ans.size(); ++i)
    printf("%d %d\n", ans[2 * i], ans[2 * i + 1]);
  return 0;
}
