Wormholes

#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 (1001)
#define ME (2000)
struct eg{int u,v,w;}g[ME];
int n,m,d[MX],A[MX],L;
vi R[MX];
bool cn[MX];
void dfs(int u){
    if(cn[u]++)return;
    A[L++]=u;
    F((ll)R[u].size())dfs(R[u][i]);
}
bool bf(){
    int u,v,X(0);
    F(n-1)F(m)
        if(d[u=g[i].u]+g[i].w<d[v=g[i].v])
            d[v]=d[u]+g[i].w;
    F(m)if(d[u=g[i].u]+g[i].w<d[v=g[i].v])
        X=1,d[v]=d[u]+g[i].w,dfs(u);
    return X;
}
void clr(){
    CL(cn,L=m=0);
    F(n)d[i]=INF,R[i].clear();
}
#define AD(A,B,C) (g[i]={B,A,C},R[B].PB(A),++m)
int main(void){
    int N,M,a,b,c;
    IN(tt)F(tt){
        scanf("%d%d",&N,&M);
        clr(),n=N;
        F(M)scanf("%d%d%d",&a,&b,&c),AD(a,b,c);
        printf("%spossible\n",bf()?"":"not ");
    }
    return 0;
}