good题解!

#include<bits/stdc++.h>
using namespace std;
int main(){
long long n;
cin>>n;
for(int i=1;i<=n;++i){
if(i%2==0){
cout<<i-1<<" ";
}
else if(i%2!=0){
cout<<i+1<<" ";
}
}
return 0;
}