#include <bits/stdc++.h>
#define fastio ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define endl '\n'
#define int long long
#define all(v) v.begin(), v.end()
//#define x first
//#define y second

using namespace std;
typedef pair<int, int> PII;

const int N = 1e5 + 10;

void solve() {
    int a,b,c;
    cin>>a>>b>>c;
    cout<<2*a<<endl;
    for(int i=1;i<=2*a;i++) cout<<i<<' ';
}
signed main() {
    fastio;
    int T;
 T = 1;
    // cin>>T;
    while (T--) solve();

    return 0;
}