#include<bits/stdc++.h> 
using namespace std;
void hannuo(int n,char a,char b,char c){
	if(n==1) cout<<a<<"->"<<c<<endl;
	else{
		hannuo(n-1,a,c,b);
		cout<<a<<"->"<<c<<endl;
		hannuo(n-1,b,a,c);
	}
}
int main(){
	int n;
	cin>>n;
	hannuo(n,'A','B','C');
	return 0;
}

https://theuselessweb.com https://puginarug.com https://optical.toys/thatcher-effect/ https://memory.toys/classic/medium/ https://maze.toys/mazes/mini/daily/ https://cursoreffects.com/ 好玩网站

#include<iostream> 
using namespace std; 
int main(){ 
  int n,sum=0; 
  cin>>n; 
  for(int i=1;i<=n;++i){ 
    sum=sum+i; 
  } 
  cout<<sum; 
  return 0; 
}