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1278.cpp
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1278.cpp
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#include <cstdio>
#include <vector>
using namespace std;
int N,visit[1000000],ansn;
vector<int> cur,ans;
void sol(int n,int m){
if(n!=0&&m==0&&n>ansn){
ansn=n;
ans=cur;
return;
}
for(int i=0;i<N;i++){
if(((1<<i)&m)>0){
int k=(~(1<<i))&m;
if((n!=0&&k==0)||!visit[k]){
visit[k]=1;
cur.push_back(i);
sol(n+1,k);
cur.pop_back();
}
}
if(((1<<i)&m)==0){
int k=(1<<i)|m;
if(!visit[k]){
visit[k]=1;
cur.push_back(i);
sol(n+1,k);
cur.pop_back();
}
}
}
}
int main(){
scanf("%d",&N);
sol(0,0);
printf("%d\n",ansn-1);
for(auto a : ans) printf("%d ",a+1);
}