#include <bits/stdc++.h>
#define ve vector<int>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define pi pair<int,int>
#define all(v) v.begin(),v.end()
#define si(v) (int)v.size()
#define en '\n'
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int N = 2e5 + 228;
const int big = 1e9;
int n, m;
ve g[N];
int main(){
iostream::sync_with_stdio(false); cin.tie(0); ios_base::sync_with_stdio(false); cout.tie(0);
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
cin >> n >> m;
for (int i = 1; i <= n; i++){
int a, b;
cin >> a >> b;
g[a].pb(b);
}
cout << m << en;
for (int i = 1; i <= n; i += 2){
cout << i << ' ';
}
return 0;
}
