#include<bits/stdc++.h>
using namespace std;
int main() {
	//1、计算字符串长度
	string source = "1234567890";
	int size=source.length();
	cout << size << endl;
	//2、循环组装
	string target="";
	while(true) {
		//出口条件
		if(source.length()==0) {
			break;
		}
		target=target+source[0];
		source=source.substr(1,source.length()-1);
		if(source.length()>=2) {
			source=source.substr(2,source.length()-2)+source.substr(0 , 2);
		}
		cout<<"source:"<<source<<endl;
		cout<<"target:"<<target<<endl;
		cout<<endl;
	}
	cout<<target<<endl;
	return 0;
}