#include<bits/stdc++.h>
using namespace std;

#define ull unsigned long long
#define pb push_back
#define mem(arr,val)    memset(arr,val,sizeof(arr))
#define mp make_pair
#define pii pair<int,int>
#define F first
#define S second
#define sz(x) (int)(x).size()
#define nopos string::npos
#define fr(i,a,b) for(i=a;i<=b;i++)
#define frn(i,a,b) for(i=a;i>=b;i--)

int t,n,m,x,k;
vector<int> edge[100000+7];
int level[100000+7];
bool visited[100000+7];
bool fl=0;

void bfs(int u)
{
    int i;
    queue<int> q;
    q.push(u);
    visited[u]=1;

    while(!q.empty())
    {
        u=q.front();
        q.pop();

        if(edge[u].size()==0)
        {
            if(level[u]%2==1)
                fl=1;
        }

        int flag=0;

        for(i=0; i<edge[u].size(); i++)
        {
            int v=edge[u][i];
            if(visited[v]==0)
            {
                flag=1;
                visited[v]=1;
                level[v]=level[u]+1;
                q.push(v);
            }

        }

    }
}

int main()
{
    int i,j,p;

    cin>>t;
    fr(i,1,t)
    {
        fl=0;
        scanf("%d %d %d",&n,&m,&x);

        memset(visited,0,sizeof(visited));

        while(m--)
        {
            int u,v;
            scanf("%d %d",&u,&v);
            edge[u].pb(v);
        }



        for(j=0; j<edge[x].size(); j++)
        {
            memset(visited,0,sizeof(visited));

            visited[x]=1;
            level[edge[x][j]]=1;

            bfs(edge[x][j]);

            if(fl)
                break;
        }
        printf("Case %d: ",i);
        printf(fl?"Yes\n":"No\n");

    }

    return 0;
}