#include<iostream>
#define MAX 100001
using namespace std;
int flg[MAX];
int par[MAX];
//int find(int x){
//    if (par[x] == x)
//        return x;
//    return par[x] = find(par[x]);
//}
int find(int x){//路径压缩查找
    int r = x;
    while (par[r] != r)r = par[r];
    int i = x, j;
    while (i != r){
        j = par[i];
        par[i] = r;
        i = j;
    }
    return par[x];
}
int main()
{
    int a, b, cnt = 0, num = 0;
    bool qualified = true;
    memset(flg, 0, sizeof(flg));
    for (int i = 1; i < MAX; i++)par[i] = i;
    while (cin >> a >> b,a!=-1,b!=-1){
        cnt++;//记录边的数量
        flg[a] = flg[b] = 1;
        if (a == 0 && b == 0){
            num = 0;//找一共有几个顶点
            for (int i = 1; i < MAX; i++){
                if (flg[i] == 1)num++;
            }
            //cout << num << "," << cnt << endl;//+++
            if (num == 0){//坑爹的测试数据，0 0 也是yes
                cout << "Yes";
            }
            else if (qualified && cnt==num){//顶点数一定是边数+1，因为结束时0 0cnt也加1了所以就直接==判断了
                cout << "Yes";
            }
            else{
                cout << "No";
            }
            cout << endl;
            cnt = 0; num = 0;
            qualified = true;
            memset(flg, 0, sizeof(flg));
            for (int i = 1; i < MAX; i++)par[i] = i;
            continue;
        }
        a = find(a); b = find(b);
        if (a == b)qualified = false;
        else { par[a] = b; }
    }
    return 0;
}