#include<cstdio>
#include<queue>
using namespace std;

const int N=20+5;

int ch[N][2],vis[N];

int bfs(int s)
{
    queue<int> q;
    q.push(s);
    int pre=1,last;
    while(!q.empty())
    {
        int u=q.front();
        last=u;
        q.pop();
        if(!ch[u][0]&&
 
ch[u][1]) return 0;
        if(ch[u][0]&&ch[u][1]&&!pre) return 0;
        if(!ch[u][0]&&!ch[u][1]||ch[u][0]&&!ch[u][1]) pre=0;
        if(ch[u][0]) q.push(ch[u][0]);
        if(ch[u][1]) q.push(ch[u][1]);
    }
    return last;
}

int main()
{
    int n;scanf("%d",&n);
    for
 
(int i=1;i<=n;i++)
    {
        char s1[10],s2[10];
        scanf("%s%s",s1,s2);
        if(s1[0]!='-') sscanf(s1,"%d",&ch[i][0]),ch[i][0]++,vis[ch[i][0]]=1;
        if(s2[0]!='-') sscanf(s2,"%d",&ch[i][1]),ch[i][1]++,vis[ch[i][1]]=1;
    }
    int rt;
    for(int i=1;i<=n;i++)
        if(!vis[
 
i])
            rt=i;
    int now=bfs(rt);
    if(now) printf("YES %d",now-1);
    else printf("NO %d",rt-1);
    return 0;
}