学步园

/*
分别对x,y,z topsort就ok了
注意有公共部分的时候的建边
*/
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <cstring>
#include <map>
#include <vector>
#include <cmath>
#include<queue>
using namespace std;
int n,r;
char s[3];
int x,y;
int inx[1009*2];
int iny[1009*2];
int inz[1009*2];
int ansx[1009*2],ansy[1009*2],ansz[1009*2];
vector<int> vx[1009*2],vy[1009*2],vz[1009*2];
void init()
{
    memset(inx,0,sizeof(inx));
    memset(iny,0,sizeof(iny));
    memset(inz,0,sizeof(inz));
    for(int i=1;i<=2*n;i++)
    {
        vx[i].clear();
        vy[i].clear();
        vz[i].clear();
    }
}
bool solve(int *inx,vector<int> vx[],int ansx[])
{
    queue<int> q;
    int num=0;
    for(int i=1;i<=2*n;i++)
    if(inx[i]==0)
    {
        q.push(i);
    }
    while(!q.empty())
    {
        int x=q.front();q.pop();
        ansx[x]=++num;
        for(int i=0;i<vx[x].size();i++)
        {
            int f=vx[x][i];
            inx[f]--;
            if(inx[f]==0)
            {
                q.push(f);
           }
        }
    }
    if(num==2*n)return 1;
    return 0;
}
int main()
{
    int ca=1;
    while(scanf("%d%d",&n,&r),n+r)
    {
        init();
        for(int i=1;i<=n;i++)
        {
            vx[i].push_back(i+n);
            inx[i+n]++;

            vy[i].push_back(i+n);
            iny[i+n]++;

            vz[i].push_back(i+n);
            inz[i+n]++;
        }
        for(int i=0;i<r;i++)
        {
            scanf("%s%d%d",s,&x,&y);
            if(s[0]=='I')
            {
               vx[x].push_back(y+n);
               vx[y].push_back(x+n);
               inx[y+n]++;
               inx[x+n]++;

               vy[x].push_back(y+n);
               vy[y].push_back(x+n);
               iny[y+n]++;
               iny[x+n]++;

               vz[x].push_back(y+n);
               vz[y].push_back(x+n);
               inz[y+n]++;
               inz[x+n]++;
            }
            else if(s[0]=='X')
            {
                inx[y]++;
                vx[x+n].push_back(y);
            }
            else if(s[0]=='Y')
            {
                iny[y]++;
                vy[x+n].push_back(y);
            }
            else if(s[0]=='Z')
            {
                inz[y]++;
                vz[x+n].push_back(y);
            }
        }
        int flag=1;
        if(!solve(inx,vx,ansx)){flag=0;}
        if(!solve(iny,vy,ansy)){flag=0;}
        if(!solve(inz,vz,ansz)){flag=0;}

        printf("Case %d: ",ca++);
        if(!flag){puts("IMPOSSIBLE");puts("");continue;}
        {
            puts("POSSIBLE");
            for(int i=1;i<=n;i++)
            {
                printf("%d %d %d %d %d %d\n",ansx[i],ansy[i],ansz[i],ansx[i+n],ansy[i+n],ansz[i+n]);
            }
            puts("");
        }
    }
    return 0;
}