#include <bits/stdc++.h>
using namespace std;
const int dy[] = {-1, 0, 1, 0}, dx[] = {0, 1, 0, -1};
const double EPS = 1e-8;
const double PI = acos(-1.0);
int popcount(int n) { return __builtin_popcount(n); }
int popcount(long long n) { return __builtin_popcountll(n); }
template <class T>
int SIZE(T a) {
  return a.size();
}
template <class T>
string IntToString(T num) {
  string res;
  stringstream ss;
  ss << num;
  return ss.str();
}
template <class T>
T StringToInt(string str) {
  T res = 0;
  for (int i = 0; i < SIZE(str); i++) res = (res * 10 + str[i] - '0');
  return res;
}
template <class T>
T gcd(T a, T b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <class T>
T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
template <class T>
void PrintSeq(T &a, int sz) {
  for (int i = 0; i < sz; i++) {
    cout << a[i];
    if (sz == i + 1)
      cout << endl;
    else
      cout << ' ';
  }
}
bool EQ(double a, double b) { return abs(a - b) < EPS; }
void fastStream() {
  cin.tie(0);
  std::ios_base::sync_with_stdio(0);
}
vector<string> split(string str, char del) {
  vector<string> res;
  for (int i = 0, s = 0; i < SIZE(str); i++) {
    if (str[i] == del) {
      if (i - s != 0) res.push_back(str.substr(s, i - s));
      s = i + 1;
    } else if (i == SIZE(str) - 1) {
      res.push_back(str.substr(s));
    }
  }
  return res;
}
int N, M;
int froms[100001];
int tos[100001];
bool used[100001];
vector<int> lists[100001];
int main() {
  vector<int> ans;
  cin >> N >> M;
  for (int i = 0; i < M; i++) {
    int r, c;
    cin >> r >> c;
    r--;
    c--;
    froms[i] = N - 1 - r;
    tos[i] = c;
    lists[tos[i]].push_back(i);
  }
  priority_queue<pair<int, int> > pq;
  for (int i = N - 1; i >= 0; i--) {
    for (int j = 0; j < (int)lists[i].size(); j++) {
      int idx = lists[i][j];
      pq.push(pair<int, int>(froms[idx], idx));
    }
    while (pq.size()) {
      pair<int, int> p = pq.top();
      pq.pop();
      int idx = p.second;
      if (froms[idx] > i) continue;
      ans.push_back(idx + 1);
      break;
    }
  }
  sort(ans.begin(), ans.end());
  cout << ans.size() << endl;
  for (int i = 0; i < (int)ans.size(); i++) cout << ans[i] << " ";
  cout << endl;
  return 0;
}
