//Bismillahir Rahmanir Rahim
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <cctype>
#include <cstdlib>
#include <vector>
#include <string>
#include <cstring>
#include <queue>
#include <set>
#include <stack>
#include <map>
#include <sstream>
using namespace std;
long long ar[100005],pr[100005],visitpos[4][100005],visitneg[4][100005],totpos[100005],totneg[100005],done[5][100005],flag;
vector<long long>adjpos[100005],adjneg[100005];
long long dfs(long long curr)
{
    //cout<<curr<<" ";
    long long a,s,d,f,g,h,j,k,l;
    done[flag][abs(curr)]=1;
    if(curr>0)
    {
        if(visitneg[flag][curr]) return 0;
        if(visitpos[flag][curr]) return 1;
        visitpos[flag][curr]=1;
        a=totpos[curr];
        for(s=0;s<a;s++)
        {
            d=adjpos[curr][s];
            f=dfs(-d);
            if(f==0) return 0;
        }
        return 1;
    }
    else
    {
        if(visitpos[flag][-curr]) return 0;
        if(visitneg[flag][-curr]) return 1;
        visitneg[flag][-curr]=1;
        a=totneg[-curr];
        for(s=0;s<a;s++)
        {
            d=adjneg[-curr][s];
            f=dfs(-d);
            if(f==0) return 0;
        }
        return 1;
    }
}
int main()
{
    long long a,s,d,f,g,h,j,k,l,ss;
    cin>>a;
    for(ss=1;ss<=a;ss++)
    {
        cin>>s>>d;
        for(j=0;j<=s+2;j++)
        {
            adjpos[j].clear();
            adjneg[j].clear();
            totneg[j]=0;
            totpos[j]=0;
            visitpos[1][j]=0;
            visitneg[1][j]=0;
            visitpos[2][j]=0;
            visitneg[2][j]=0;
            done[1][j]=0;
            done[2][j]=0;
        }
        for(g=1;g<=d;g++)
        {
            scanf("%lld%lld",&ar[g],&pr[g]);
            if(ar[g]>0)
            {
                totpos[ar[g]]++;
                adjpos[abs(ar[g])].push_back(pr[g]);
            }
            else
            {
                totneg[-ar[g]]++;
                adjneg[abs(ar[g])].push_back(pr[g]);
            }
            swap(ar[g],pr[g]);
            if(ar[g]>0)
            {
                totpos[ar[g]]++;
                adjpos[abs(ar[g])].push_back(pr[g]);
            }
            else
            {
                totneg[-ar[g]]++;
                adjneg[abs(ar[g])].push_back(pr[g]);
            }
        }
        //cout<<"dkjs\n";
        k=1;
        for(l=1;l<=s;l++)
        {
            //cout<<l<<" jdvjsd\n";
            if(done[1][l] || done[2][l]) continue;
            flag=1;
            if(dfs(l)==0)
            {
                flag=2;
                if(dfs(-l)==0)
                {
                    k=0;
                    break;
                }
            }
        }
        if(k) printf("Case %lld: Yes\n",ss);
        else printf("Case %lld: No\n",ss);
    }
}