#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<vector>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<string>
#include<math.h>
#include<cctype>
#define ll long long
#define REP(i,a,b) for(int (i)=(a);(i)<=(b);(i)++)
#define REPP(i,a,b,t) for(int (i)=(a);(i)<=(b);(i)+=(t))
#define rep(i,a,b) for(int (i)=(a);(i)>=(b);(i)--)
#define repp(i,a,b,t) for(int (i)=(a);(i)>=(b);(i)-=(t))
#define PII pair<int,int>
#define fst first
#define snd second
#define MP make_pair
#define PB push_back
#define RI(x) scanf("%d",&(x))
#define RII(x,y) scanf("%d%d",&(x),&(y))
#define RIII(x,y,z) scanf("%d%d%d",&(x),&(y),&(z))
#define DRI(x) int (x);scanf("%d",&(x))
#define DRII(x,y) int (x),(y);scanf("%d%d",&(x),&(y))
#define DRIII(x,y,z) int (x),(y),(z);scanf("%d%d%d",&(x),&(y),&(z))
#define RS(x) scanf("%s",x)
#define RSS(x,y) scanf("%s%s",x,y)
#define DRS(x) char x[maxn];scanf("%s",x)
#define DRSS(x,y) char x[maxn],y[maxn];scanf("%s%s",x,y)
#define MS0(a) memset((a),0,sizeof((a)))
#define MS1(a) memset((a),-1,sizeof((a)))
#define MS(a,b) memset((a),(b),sizeof((a)))
#define ALL(v) v.begin(),v.end()
#define SZ(v) (int)(v).size()

using namespace std;

const int maxn=1000100;
const int INF=(1<<29);
const double EPS=0.0000000001;
const double Pi=acos(-1.0);

int u,v;
int fa[maxn];
bool flag;
vector<int> V;
bool vis[maxn];

void Init()
{
    flag=1;
    REP(i,1,maxn-1) fa[i]=i;
    MS0(vis);
    V.clear();
}
/*
int find(int x)
{
    return fa[x]==x?x:fa[x]=find(fa[x]);
}
*/
int find(int x)
{
    int p=x,t;
    while(fa[p]!=p) p=fa[p];
    while(x!=p){
        t=fa[x];
        fa[x]=p;
        x=t;
    }
    return x;
}

void solve()
{
    if(flag&&SZ(V)){
        int x=find(V[0]);
        REP(i,0,SZ(V)-1){
            int y=find(V[i]);
            if(x!=y){
                flag=0;break;
            }
        }
    }
    puts(flag?"Yes":"No");
}

int main()
{
    freopen("in.txt","r",stdin);
    Init();
    while(~RII(u,v)){
        if(u==-1&&v==-1) return 0;
        if(u==0&&v==0){
            solve();
            Init();
            continue;
        }
        if(!vis[u]) V.PB(u),vis[u]=1;
        if(!vis[v]) V.PB(v),vis[v]=1;
        int x=find(u),y=find(v);
        if(x==y) flag=0;
        else fa[x]=y;
    }
    return 0;
}