#include <bits/stdc++.h>
using namespace std;
const long long md = 1e9 + 7;
const long long MX = 2e5 + 5;
const long long INF = 1e18;
const long double PI = 4 * atan((long double)1);
long long power_md(long long a, long long n) {
  long long res = 1;
  while (n) {
    if (n % 2) res = (res % md * a % md) % md;
    a = (a % md * a % md) % md;
    n /= 2;
  }
  res %= md;
  return res;
}
long long power(long long a, long long n) {
  long long res = 1;
  while (n) {
    if (n % 2) res *= a;
    a = a * a;
    n /= 2;
  }
  return res;
}
long long abst(long long a) { return ((a < 0) ? (-1 * a) : (a)); }
class cmp_set {
 public:
  bool operator()(long long a, long long b) { return a > b; }
};
vector<string> vec_splitter(string s) {
  s += ',';
  vector<string> res;
  while (!s.empty()) {
    res.push_back(s.substr(0, s.find(',')));
    s = s.substr(s.find(',') + 1);
  }
  return res;
}
void debug_out(vector<string> __attribute__((unused)) args,
               __attribute__((unused)) long long idx,
               __attribute__((unused)) long long LINE_NUM) {
  cerr << endl;
}
template <typename Head, typename... Tail>
void debug_out(vector<string> args, long long idx, long long LINE_NUM, Head H,
               Tail... T) {
  if (idx > 0)
    cerr << ", ";
  else
    cerr << "Line(" << LINE_NUM << ") ";
  stringstream ss;
  ss << H;
  cerr << args[idx] << " = " << ss.str();
  debug_out(args, idx + 1, LINE_NUM, T...);
}
int32_t main() {
  long long n, m;
  cin >> n >> m;
  long long minn = 1e12;
  for (long long i = 0; i < m; i++) {
    long long l, r;
    cin >> l >> r;
    minn = min(minn, (r - l));
  }
  cout << (minn + 1) << "\n";
  long long arr[n];
  for (long long i = 0; i <= minn; i++) arr[i] = i;
  for (long long i = minn + 1; i < n; i++) {
    arr[i] = arr[i - (minn + 1)];
  }
  for (long long i = 0; i < n; i++) cout << arr[i] << " ";
  cout << "\n";
  return 0;
}
