Largest Clique

#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define ZERO (1e-10)
#define INF (1<<29)
#define CL(A,I) (memset(A,I,sizeof(A)))
#define DEB printf("DEB!\n");
#define D(X) cout<<"  "<<#X": "<<X<<endl;
#define EQ(A,B) (A+ZERO>B&&A-ZERO<B)
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
#define IN(n) int n;scanf("%d",&n);
#define FOR(i, m, n) for (int i(m); i < n; i++)
#define REP(i, n) FOR(i, 0, n)
#define F(n) REP(i, n)
#define FF(n) REP(j, n)
#define FT(m, n) FOR(k, m, n)
#define aa first
#define bb second
void ga(int N,int *A){F(N)scanf("%d",A+i);}
#define MX (1024)
vi g[MX],G[MX],e[MX],R[MX];
int cn[MX],C[MX],I[MX],H[MX],L,S[MX];
void CLR(int N=MX){CL(S,L=0);F(N)g[i].clear(),e[i].clear(),G[i].clear(),R[i].clear(),cn[i]=I[i]=0;}
void dfs1(int x){
    cn[x]=1;
    for(auto h:g[x])if(!cn[h])dfs1(h);
    H[L++]=x;
}
void dfs2(int x,int c){
    cn[x]=0,C[x]=c;
    for(auto h:e[x])if(cn[h])dfs2(h,c);
}
#define ADD(A,B) (g[A].PB(B),e[B].PB(A))
int ini(int N){
    F(N)if(!cn[i])dfs1(i);
    int I(0);
    for(int i(L-1);~i;--i)if(cn[H[i]])dfs2(H[i],++I);
    F(N)++S[C[i]-1];
    F(N)for(auto&h:g[i])if(C[i]!=C[h])G[C[i]-1].PB(C[h]-1),R[C[h]-1].PB(C[i]-1);
    F(I)sort(G[i].begin(),G[i].end()),unique(G[i].begin(),G[i].end());//+/-
    return I;
}
int N,M,a,b,X,dp[MX];
int dfs(int u){
    int &v(dp[u]);
    if(~v)return v;
    v=S[u];
    for(auto&h:G[u])v=max(v,dfs(h)+S[u]);
    return v;
}
int main(void){
    IN(tt)F(tt){
        scanf("%d%d",&N,&M);
        CLR(N),X=0,CL(dp,-1);
        F(M)scanf("%d%d",&a,&b),--a,--b,ADD(a,b);
        N=ini(N);
        F(N)X=max(X,dfs(i));
        printf("%d\n",X);
    }
    return 0;
}