#define mp(a,b) make_pair(a,b)
#define mem(a,b) memset(a,b,sizeof(a))
#define LL long long
#define lson step<<1
#define rson step<<1|1
#define MOD 1000000009
#define sqr(a) ((a)*(a))
using namespace std;
int pre[N],r[N];
int n,q;
int K,num[N];
char ope[1000];
vector
void Init()
{
for(int i=0;i<=n;i++) pre[i]=i,r[i]=0;
}
int find(int x)
{
if(x!=pre[x])
{
int f=pre[x];
pre[x]=find(pre[x]);
r[x]^=r[f];
}
return pre[x];
}
bool Union(int a,int b,int c)
{
int ra=find(a),rb=find(b);
if(ra==rb)
{
if((r[a]^r[b])!=c) return false;
else return true;
}
if(ra==n) swap(ra,rb); //这句很重要，关系到Query的那个判断，WA了几次
pre[ra]=rb;
r[ra]=r[a]^r[b]^c;
return true;
}
int Query()
{
bool vis[N];mem(vis,false);
int ans=0;
for(int i=0;i
if(vis[i])continue;
int cnt=0;
int root=find(num[i]);
if(!vis[j]&&find(num[j])==root)
{
cnt++;
vis[j]=true;
ans^=r[num[j]];
}
}
if(root!=n&&cnt&1) return -1;
}
return ans;
}
int main()
{
int CAS=0;
while(scanf("%d%d",&n,&q)!=EOF)
{
if(n==0&&q==0) break;
printf("Case %d:\n",++CAS);
Init();
bool error=false;
int cas=0;
while(q--)
{
scanf("%s",ope);
if(ope[0]=='I')
{
getchar();gets(ope);cas++;
int space=0,u,v,w;
for(int i=0;i
else sscanf(ope,"%d%d%d",&u,&v,&w);
if(error) continue;
if(!Union(u,v,w)){printf("The first %d facts are conflicting.\n",cas);error=true;}
}
else
{
scanf("%d",&K);
for(int i=0;i
int ans=Query();
if(ans==-1) puts("I don't know.");
else printf("%d\n",ans);
}
}
puts("");
}
return 0;
}