sicily1021-couples

//简单利用栈的功能解决就好
//开始时候录入cp关系可以利用数组录入相应的关系
#include "iostream"
#include "stack"
#include "cstring"
using namespace std;

int main(){
    int c;
    int couple[200002];
    while(cin>>c&&c!=0){
        stack<int>s;
        memset(couple,0,sizeof(couple));
        for (int i = 0; i < c; ++i)
        {
            int t,x;
            cin>>t>>x;
            couple[t]=x;
            couple[x]=t;
        }
        for (int i = 1; i <= 2*c; ++i)
        {
            if(!s.empty()&&s.top()==couple[i]){
                s.pop();
            }else{
                s.push(i);
            }
        }
        if(s.empty()){
            cout<<"Yes"<<endl;
        }else{
            cout<<"No"<<endl;
        }
    }
}