#include<iostream>
using namespace std;
void swap(int& a,int& b){
int t=a;
a=b;
b=t;
}
int main(){
int a,b;
while(cin>>a>>b){
swap(a,b);
cout<<a<<b<<endl;
}
return 0;
}原文：https://www.cnblogs.com/mch5201314/p/9391691.html