1390 - Weight Comparison

#include <bits/stdc++.h>
#define SYN ios_base::sync_with_stdio(0);cin.tie(0);
using namespace std;
/***************************************************************************************************************************************/
typedef long long int LLI;
typedef unsigned long long int ULLI;
#define IMAX ((unsigned)1<<31)-1
#define eps 1e-11
#define LIMAX (1LL<<63)-1
#define ULIMAX (1LL<<64)-1
#define UIMAX ((LLI)1<<32)-1
#define MP(X,Y) make_pair(X,Y)

#define REP(i,n) for(int i=0;i<n;i++)
#define DREP(i,n) for(int i=n;i>=0;i--)
#define LREP(i,a,b) for(int i=a;i<=b;i++)
#define DLREP(i,a,b) for(int i=a;i>=b;i--)
#define FOR(i,a,b,c) for(int i=a;i<=b;i+=c)

#define fill(a,v) memset(a,v,sizeof(a))
#define DEBUG(x) cout << #x << ": " << x << endl;
#define SZ(X) ((int)X.size())
#define all(x) (x).begin(),(x).end()
#define SORT(x) sort(all(x))
#define VI vector<int>
#define VS vector<string>
#define PB push_back
#define REV(a) reverse(all(a))
typedef pair<int, int>PII;
typedef pair<LLI, LLI>PLL;
typedef pair<char, int>PCI;
typedef pair<int, char>PIC;
typedef pair<double, double>PDD;
#define MSI map<string,int>
#define MSLI map<string,LLI>
#define MCI map<char,int>
template<class T> inline T MIN_3(T a, T b, T c)
{
    return min(min(a, b), c);
}
template<class T> inline T MAX_3(T a, T b, T c)
{
    return max(max(a, b), c);
}
#define ACM(x) accumulate(all(x),0);
#define CAP(x,y,z) set_intersection (all(x), all(y), z.begin())
#define CUP(x,y,z) set_union(all(x),all(y),z.begin())
#define DIF(x,y,z) set_difference (all(x),all(y),z.begin());
#define BRPS(n,bit) bitset<bit>(n)
#define DSORT(X)  sort(X.rbegin(), X.rend());
#define read(x) freopen(#x".txt","r",stdin)
#define write(x) freopen(#x".txt","w",stdout)
#define LB(A, x) (lower_bound(all(A), x) - A.begin())//exactly where it starts
#define UB(A, x) (upper_bound(all(A), x) - A.begin())
#define UNQ(x) SORT(x),(x).erase(unique(all(x)),x.end())

template<class T> inline T BIGMOD(T n, T m, T mod)
{
    LLI ans = 1;
    LLI k = n;
    while(m)
    {
        if(m & 1)
        {
            ans *= k;
            if(ans>mod) ans %= mod;
        }
        k *= k;
        if(k>mod) k %= mod;
        m >>= 1;
    }
    return ans;
}


inline int DBLCMP(double a, double b)
{
    if(fabs(a - b) <= eps) return 0;
    if(a < b) return -1;
    return 1;
}
template<class T> inline T sqr(T x)
{
    return x*x;
}
template<class T> inline int countbit(T n)
{
    return (n == 0) ? 0 : (1 + countbit(n&(n - 1)));
}
template<class T> inline T euclide(T a, T b, T &x, T &y)
{
    if (a < 0)
    {
        T d = euclide(-a, b, x, y);
        x = -x;
        return d;
    }
    if (b < 0)
    {
        T d = euclide(a, -b, x, y);
        y = -y;
        return d;
    }
    if (b == 0)
    {
        x = 1;
        y = 0;
        return a;
    }
    else
    {
        T d = euclide(b, a % b, x, y);
        T t = x;
        x = y;
        y = t - (a / b) * y;
        return d;
    }
}
template<class T> string toString(T n)
{
    ostringstream ost;
    ost << n;
    ost.flush();
    return ost.str();
}
template<class T> string toBinary(T n)
{
    string ret="";
    while(n)
    {
        if(n%2==1)ret+='1';
        else ret+='0';
        n>>=1;
    }
    reverse(ret.begin(),ret.end());
    return ret;
}
void combination(int n,vector< vector<int> > &ret)
{
    ret.resize(n+1, vector<int>(n+1, 0));
    for(int i=1; i<=n; i++)
    {
        ret[i][0]=ret[i][i]=1;
        for(int j=1; j<i; j++)
        {
            ret[i][j]=ret[i-1][j]+ret[i-1][j-1];
        }
    }
}
int toInt(string s)
{
    int r = 0;
    istringstream sin(s);
    sin >> r;
    return r;
}
LLI toLInt(string s)
{
    LLI r = 0;
    istringstream sin(s);
    sin >> r;
    return r;
}
double toDouble(string s)
{
    double r = 0;
    istringstream sin(s);
    sin >> r;
    return r;
}
vector<string> parse(string temp)
{
    vector<string> ans;
    ans.clear();
    string s;
    istringstream iss(temp);
    while (iss >> s)ans.PB(s);
    return ans;
}
template<class T> inline T gcd(T a, T b)
{
    if (a < 0)return gcd(-a, b);
    if (b < 0)return gcd(a, -b);
    return (b == 0) ? a : gcd(b, a % b);
}
template<class T> inline T lcm(T a, T b)
{
    if (a < 0)return lcm(-a, b);
    if (b < 0)return lcm(a, -b);
    return a*(b / gcd(a, b));
}
template<class T> inline T power(T b, T p)
{
    if (p < 0)return -1;
    if (b <= 0)return -2;
    if (!p)return 1;
    return b*power(b, p - 1);
}
#define fst first
#define snd second
//istringstream(temp) >> data >> value >> stamp;
//mod1 = 1000000007, mod2 = 1000000009;
//.016-.040-.900-2.48
/***************************************************************************************************************************************/
int N,E;
vector<int>adj[5009];
bool vis[5009];
vector<int>topo;
vector<PII>Edges;
int color[5009];
set<PII>del;
vector<PII>res;

void ini()
{
    for(int i=0;i<=5002;i++)adj[i].clear();
    fill(vis,0);
    fill(color,0);
    topo.clear();
    Edges.clear();
    del.clear();
    res.clear();

}
void topoSort(int cn)
{
    vis[cn]=true;
    REP(i,adj[cn].size())
    {
        if(!vis[adj[cn][i]])topoSort(adj[cn][i]);
    }
    topo.PB(cn);
}

void dfs(int cn)
{
    color[cn]=1;
    int now;
    REP(i,adj[cn].size())
    {
        now=adj[cn][i];
        if(color[now]==2)
        {
            del.insert(MP(cn,now));
        }
        else
        {
            dfs(now);
        }
    }
    color[cn]=2;
    return ;
}


int main()
{
    //SYN
    //read();
    //write();
    int kase,ks=0,a,b;
    scanf("%d",&kase);
    while(kase--)
    {
        scanf("%d %d",&N,&E);
        REP(i,E)
        {
            scanf("%d %d",&a,&b);
            adj[a].PB(b);
            Edges.PB(MP(a,b));
        }
        //topoSort(1);
        for(int i=1; i<=N; i++)
        {
            if(!vis[i]) topoSort(i);
        }
        for(int i=topo.size()-1;i>=0;i--)
        {
            if(color[topo[i]]==0)
            {
                dfs(topo[i]);
            }
        }
        for(int i=0;i<E;i++)
        {
            a=Edges[i].fst;
            b=Edges[i].snd;
            if(del.find(MP(a,b))!=del.end());
            else res.PB(MP(a,b));
        }
        SORT(res);
        printf("Case %d: ",++ks);
        cout << res.size() << endl;
        REP(i,res.size())
        {
            printf("%d %d\n",res[i].fst,res[i].snd);
        }
        ini();
    }
    return 0;
}